Serin Osman

"The only rule is there are no rules."

- A maxim frequently used by Osman

Admiral Serin "Oz" Osman, born Serin Çelik and formerly known as SPARTAN-019, (service number 39489-72738-SO ) is the Commander-in-Chief of the Office of Naval Intelligence, inheriting the role from Admiral Margaret Parangosky after the end of the Human-Covenant War.

Early life
Serin Çelik was born in 2511 on the colony of Cascade. Her mother, Pinar Çelik, was a prostitute and drug addict who completely neglected her daughter. On more than one occasion, young Serin resorted to digging through garbage cans for food. Numerous calls to child services were made, to no avail. The only person who cared for Serin was her teacher, Alkmini Leandro, who regularly brought food to school for her.

SPARTAN-II program and ONI career
"BB sometimes wondered what kind of operational Spartan she would have made, just the averagely terrifying kind or a full-blown angel of death."

- Black-Box

In 2517, Serin was abducted as a Spartan-II candidate by an ONI agent named Mr. Teddy. She was given the designation Serin-019 and was trained under Chief Mendez along with the rest of the candidates. Because of her living conditions, she (along with Soren-066) was not replaced with a flash clone. She often ate the other candidates' leftover food, a practice for which John-117 teased her.

Serin did not successfully complete the augmentation process, receiving only the genetic and biochemical enhancements before her body started to reject the rest. While she failed the augmentation process, she still possesses a few of the enhancements, though no skeletal augmentation. The Office of Naval Intelligence took custody of her when she was 14 years old; they repaired the damage done by the failed augmentation process, educated her further, and put her into the ONI commanders' program. The other Spartans thought her dead; unlike some of the other washouts later assigned to ONI, she was withdrawn from the program before the funeral ceremony for the Spartans killed in the augmentations. As a result, she remained unaware if the successful Spartans were even told of the fate of the failures.

Considered as a protégé to Admiral Margaret Parangosky, CINCONI, the Admiral groomed the former Spartan for a potential future as her successor. Serin considered herself the only person the Admiral would always forgive even if she failed. In order to hide her status as a former Spartan, she adopted the surname "Osman". Though people often assumed she was of Turkish descent based on her name and appearance, she did not actually know whether this was the case; though the information on her pre-Spartan identity was readily available to her, she did not look at her personal file for decades until spontaneously deciding to do so in April 2553. By 2553, Osman held the rank of captain. She was handpicked by Parangosky to lead up a black operations team known as Kilo-Five with the mission to ensure a Sangheili insurgency, keeping the Elites from threatening humanity. The team was composed of the civilian professor and Sangheili expert Evan Phillips; ODSTs Staff Sergeant "Mal" Geffen, Sergeant Lian Devereaux, and Corporal "Vaz" Beloi; and Spartan-II Naomi-010.

Meeting the Bishop
"Just remember that my enemy's enemy isn't my friend, Professor. He's my enemy who's just taking a sidebar."

- Osman stops just short of confirming to Evan Phillips ONI's underhanded intentions in working with the Servants of the Abiding Truth. Evan Phillips was tasked with connecting Osman to dissident Sangheili who were likely to try to disrupt any formal peace deals between the UEG and the Arbiter. His efforts resulted in a January meeting on the glassed world of New Llanelli with Avu Med 'Telcam, a representative of the Servants of the Abiding Truth. Phillips and Captain Osman took a shuttle from the to the surface. She watched from its cargo bay as Phillips spoke with the former field master first. All the while, she kept her rifle at the ready should anything go awry. Initial contact concluded, Phillips returned and informed Osman that 'Telcam, whom he identified with the honorific of "Bishop", had agreed to speak with her. The professor cautioned her to remember that the Bishop was a fundamentalist and would not take kindly to slights against his beliefs or pride. Osman made sure to take the Sangheili's sensibilities into account; introducing herself as a shipmaster. Wanting to preserve as much deniability as she could for Phillips, she asked that he give her ten minutes alone with their contact. The Sangheili, an accomplished English-speaker, made it clear that he was opposed to the Arbiter and expressed genuine confusion regarding what the UEG could hope to gain from speaking with him. To 'Telcam's great surprise, Osman not only did not flinch at his talk of killing 'Vadam, but offered to supply his faction with weapons to aid in the effort. She set about convincing him of her sincerity in this matter by arguing that though the two of them would never be friends, humans were capable gamblers and wished to support the side more likely to win. Still somewhat skeptical, 'Telcam countered that her government would seek to impose itself as the Servants' puppeteer through making them beholden to it in this fashion. She dismissed his concerns by appealing to their shared desire for stability and isolation between their peoples. If Sangheili and humans could both keep their own troublesome groups in line, they could remain apart permanently, she argued. She also found common ground in the fact that both of them would need to keep their correspondence secret from those who would wield it as a political weapon against them if discovered. Before he committed to the deal, however, 'Telcam told her he had one final condition: she and her government must cease blaspheming the gods. He begrudgingly admitted that the Halos were weapons of mass death, but saw this as no reason to charge that their creators were neither divine nor immortal. He even accused her of hypocrisy in this insofar as her own faith was concerned, as he assumed she was a Christian and followed after a god who had died and yet still presumably lived. The captain was very careful in her response, assuring him that humanity was by no means united in any particular way concerning the veneration or belief in any deities. 'Telcam didn't push the issue any further, and they parted ways with the understanding that the Servants would leave humanity alone after they deposed the Arbiter and established themselves as the rulers on Sanghelios.

Hoping this meant the UNSC wouldn't have to fight Sangheili for a good while, Osman returned to Phillips and congratulated him for setting this up. He was not in the least bit naive with respect to what ONI's plans were, but they agreed it was still best that nothing be shared with him explicitly. After settling into their seats in the shuttle, Osman ran the preflight checks before handing control over to its A.I.. She opened a secure channel through wavespace to Admiral Parangosky to let her know the mission had been a success and that they were returning. A few hours later, the shuttle rendezvoused with the Battle of Minden. Once they were aboard the larger slipspace-capable vessel, a course was charted back to Earth. Phillips casually asked Osman about Turkish restaurants in Sydney and she played along, not wishing to expose the fact that her surname was an invention and that she was still willfully unaware of where she really came from.

Assembling the team
"Time to put Kilo-Five together, then. BB, you're formally assigned to Captain Osman as of now. Lead on, Captain."

- Margaret Parangosky to Black-Box and Osman. By January 26, Serin found herself waiting outside Admiral Parangosky's offices within HIGHCOM Facility Bravo-6. Her own desk was situated near the door beyond which lay a corridor that led to the CINCONI herself. Accompanying her while she waited was the Minister for the Colonies, David Agnoli. Through he had made no appointment of his own to see Parangosky, he had no compunction about asking Osman to get him a meeting. Osman, however, made sure he knew that Parangosky calls him a weasel and when he casually began rifling through a book that had been given to her by Fleet Admiral Terrence Hood, she asked that he try to refrain from getting his greasy fingerprints all over it. At that moment, the door opened at the hand of Parangosky's flag lieutenant, a young man by the name of Dorsey. Told that the Admiral would see her then, she grabbed the files she needed from her desk and made for the door while Agnoli showed himself out. Just before she could cross the threshold, her path was suddenly filled with the holographic projection of an unremarkable blue cube. The smart A.I. introduced itself as Black-Box. Osman asked whose pet he was an continued on her way. Black-Box had to reroute himself so he could continue to make his avatar visible as she walked down the corridor, informing the captain that he worked for Parangosky. When she reached where the Admiral was seated, she remarked that it was good the two of them were already getting to know each other. Parangosky assured Osman that she could trust Black-Box with her life, if it came to that. Once the office had been secured so the three of them could speak in confidence, the Admiral in told Osman that she would in fact be taking him on as her personal A.I. for the missions that lay ahead. Given the gravity with which Parangosky was speaking, Serin couldn't help but ask whether she was referring to more than just fomenting conflict between the Sangheili. In response to this, she was informed that some recent evidence suggested Catherine Halsey was still alive. Electronic intelligence (ELINT) officers onboard the had detected massive electromagnetic abnormalities in the Zeta Doradus system where the artificial world of Onyx had been before its disassembly. ELINT could tell that something the size of a solar system was present, but yet undetectable in realspace. Onyx had been the doctor's last known location. Though the Sangheili were to still be Kilo-Five's top priority at the present, Parangosky made clear that should the Glamorgan find a way to access whatever was still there in place of Onyx, she wanted Kilo-Five on hand to apprehend Halsey if she was present. Until such an occasion arose, however, the other human members of the team were not to be told she was considered still at large. Having established the parameters of the objectives ahead of the them, the two woman and the A.I. concluded their business and resolved to meet the rest of Kilo-Five. To Osman's surprise, Parangosky let her know that just around two hours prior she had taken a gamble and invited Doctor Phillips to join, making him the only civilian on the team.

Black-Box and the two officers met the professor before the four of them continued on to Bravo-6's threat analysis wing where the rest of the team was. The Orbital Drop Shock Troopers Sergeant Lian Devereaux, Staff Sergeant Malcolm Geffen, and Corporal Vasily Beloi, and Petty Officer Naomi-010, a Spartan-II super-soldier, had been handpicked to make up Kilo-Five. Naomi was the first to notice their approach and she announced that an officer was on deck. The Spartan and marines snapped to attention until they were told to stand easy by Parangosky, who introduced them to Osman and Phillips. Everyone seated themselves amongst tables and Osman distributed six datapads to herself and her new teammates. She kept an eye on Naomi, trying to gauge whether or not the Spartan recognized her from their childhood on Reach. Naomi kept giving her furtive glances as well, not quite able to place the face but knowing she knew the woman from somewhere. After Parangosky brought everyone up to speed on the task before them, Captain Osman let them know that they would be shipping out int he morning. Any last-minute drinking would need to be done that evening within the complex. At Midpoint Anchorage, they would be transferred to the, a state-of-the-art outfitted with Forerunner technological enhancements to her SFTE.

Back to Brunel
"Lian Devereaux"

- Serin Osman The following day Naomi continued to look at Serin strangely during the shuttle transit to Midpoint. After Osman had acclimated herself to the commanding officer's seat on the Port Stanley's bridge, she gave Black-Box permission to run through the final launch checks himself and asked him whether or not everyone else was secure. He took this opportunity to warn her that Naomi was on her way to the bridge at that very moment. With only five minutes until their planned jump to slipspace, Osman was prepared for the Spartan's entrance. She asked Naomi if there was something she needed to ask her, to which she was fully straightforward regarding her perplexing familiarity with Osman's face. Serin chose then to tell her the truth about who she was. Serin-019 was alive. Opening up was a great relief to Osman, but Naomi barely reacted, simply belting in at a comms station and acknowledging that they should be heading out. Just then the rest of the team arrived on the bridge and after confirming that nobody had any issues with the arrangements on the ship so far, everyone was seated and strapped in for the jump. BB, knowing Serin's proclivities regarding jumps, offered to sedate her but she said she could deal with it, not wanting to appear weak in front of the others. Just before they slipped into another dimension, BB intercepted a databurst from the. Osman struggled when the jump finally, as was usual, and it was Devereaux who asked if she was alright. Rather than making the captain feel even worse, she made light of the issue by comparing her situation to Horatio Nelson and his seasickness. With forty-eight hours until they reached the Brunel system and New Llanelli, Osman asked BB about the transmission they had received right before jumping. He relayed that the Ariadne had been forced to drop out of slipspace near Venezia in the Orso system because of a technical problem. The ship's commander had requested permission to land nonessential personnel on the planet due to unsafe conditions aboard but the colony had refused him. The message BB picked up had been meant for Earth and was a request for advice. Any further information regarding the developing situation would have to wait until they were no longer in slipspace, so Osman resolved that if nobody else had moved to aid them by then, she wanted to know. Retiring to her cabin to soothe her headache, Serin was greeted by a bag of crystallized ginger Parangosky had arranged for her, since she knew spaceflight could make her nauseous. She popped one of the cubes in her mouth and made for the hangar bay.

With an estimated ten hours left before they arrived at New Llanelli, Osman took it upon herself to seek out the rest of her new crew for a very particular purpose. BB, having listened to conversations being had surrounding the odd tension between the captain and Naomi, had encouraged her to be transparent with everyone about her past. The A.I. preceded her arrival to inform them she had called a meeting and would be preset imminently. She met Phillips on the hangar deck and found the three ODSTs within a small stealth dropship made to look like a civilian patrol vessel. To Vaz, Phillips looked as if he had just been reprimanded in some way by Osman. She casually asked how things were going before making it clear that she was as omnipresent as BB as long as he shared information with her. Just before she appeared, Devereaux had asked Vaz if he was aware that they really didn't have a plan for their current mission. Osman rebuffed this, stating that she did have one. She explained that in light of the absence of any top-level entity in command and control of the Sangheili, the best they could do then was to hand off the weapons to see where fault lines formed. She also cautioned that given the patchy short-range comms they would be at the mercy of during the majority of their mission, the ODSTs would be engaging in more surveillance work than they would be combat, though she thought it likely there would be some of that as well. Abruptly changing the subject, she then revealed what she had intended to: that she had been in the Spartan-II program and that she and Naomi knew each other years ago. She even told them they had been been six years old when they began, and that at that young age they had been put through real boot camp, not a military academy. Naomi, who had joined the others shortly after Osman first showed up on the deck, was angered by the captain's willingness to divulge such closely-guarded secrets and couldn't keep herself from giving her an accusatory look. Between Naomi's indigence and the shocked semi-silence of the others, Osman awkwardly exited the conversation with instructions to BB regarding bringing them out of slipspace in two hours and doing a comms sweep of the sector. She jumped down from the dropship's crew bay and took the ladder up to the upper gantry, leaving the crew.

When the time to re-enter realspace arrived, Osman braced herself against her seat, grunting in discomfort. At 149 million kilometers from the star, BB calculated the rest of the transit would take around five hours, placing them well ahead of schedule. A number of messages were waiting for the crew, including a sitrep for Osman from Parangosky. Naomi asked the A.I. if he knew anything about the status of Dr. Halsey, and Osman quickly jumped in and assured the Spartan Halsey was dead. Changing the subject, she directed Phillips to take a seat at the communications console so that he could listen for any Sangheili transmissions. Vaz asked whether New Llanelli was the name of the planet they were meeting 'Telcam on or if it had just referred to the colony there, and Osman told him it was both. She asked Black-Box whether he had made contact with any of their allies in the sector, and he replied that Kilo-Three-Nine was receiving their hail. Osman explained that Kilo-Three-Nine, or Mike Spenser, an agent for the Department of Colonial Security, was working as an informant for ONI and had been living on Reynes and running his own string of Kig-Yar informers. When Spenser finally opened a live connection from the planet to them, he shared much that had been happening recently in ex-Covenant society. By his account, there was a clear lack of leadership in many places. He also had heard of a recent high-profile double-murder on Sanghelios carried out by the Servants against two keep elders for blasphemy. Osman let Spenser know that with the war over, the UNSC could take over surveillance in the sector now and that she was planning to pull him out. Next up was 'Telcam, who, after connecting with the Port Stanley despite being unable to locate the source of its signal, confirmed the meeting. They would make the exchange at the same location they had met one another previously. 'Telcam asked why she was choosing to remain hidden through stealth, and she reminded the former field master that they were not the only two parties out there. Phillips was able to eavesdrop on to the comms chatter coming from the Bishop's boarding craft and two Tarasque heavy fighters and Osman was very pleased to hear that the Elites were arguing over double-crossing the humans and were vexed over not being able to find the their ship.

Stoking one fire and cooling another
"Serin Osman"

- Vasily Beloi All members of the team save for Naomi departed the Port Stanley at 15,000 kilometers from New Llanelli in a dropship carrying an M12 Warthog, a forklift, and a trailer full of crates of tagged weapons. Osman made sure BB, who split his processes between the prowler and the dropship, kept all intercepted channels patched through to Phillips. She coordinated with Naomi to keep track of where the Sangheili were and had Devereaux set them down behind a ridge just north of an escarpment that slanted down to an ice rink of vitrified soil. After letting everyone know that they'd be heading straight for Spenser on Reynes after concluding their business there, Phillps asked if a replacement would be needed for him, but Osman dismissed his offer. Upon landing, she rolled up her sleeves and helped Devereaux hitch the trailer to the Warthog. From a vantage point on the ridge Mal used an SRS99D-S2 AM sniper rifle to keep she and the others informed about the other shore party. Serin took the Warthog's wheel and drove she, Vaz, and Phillips three hundred meters to stop just thirty meters from 'Telcam, another Sangheili, and two Jiralhanae. Before exiting the vehicle, she implored Vaz to let 'Telcam get away with the weapons no matter what happened. Dressed in a black UNSCN flight suit and light infantry armor to appear less threatening, she took the lead in meeting the Bishop, explaining that they had brought him an assortment of Type-25 plasma rifles, Type-1 plasma grenades, and antipersonnel mines. She also assured him that there would be more to come and that she could even take requests. The Bishop called her bluff at this, since they both knew it wasn't as if she could procure warships for him, and took the opportunity to ask one more where their ship was presently hidden. Osman once again rejected the inquiry but was keen to notice that it seemed as if he was truly looking for a new craft. They concluded the exchange and Osman promised they would see one another in just a week to do it again. The humans stayed put until the Servants' dropship had taken off. Phillps let Osman know that 'Telcam still didn't trust them, as evidently a discussion was being had about whether the humans would warn the Arbiter. This didn't concern her, as she had no plans to do anything of the like. Vaz offered to steer them back to where Dev waited for them and Osman consented, stepping up to the back hatch to man the M41 Vulcan LAAG.

Before they could leave New Llanelli behind, Mal spotted a lone human approaching them. This unexpected appearance and the complication it brought greatly annoyed Captain Osman and Vaz took her aside after they stopped the Warthog near him to ask that he not be harmed. The emaciated man identified himself as Tom Muir and said he was the only survivor from the colony's glassing seven years prior. Osman agreed to take him with them as far as the closest UNSC base, provided he was confined to quarters on the Port Stanley. Before making the jump to Reynes, Osman set up a connection with Parangosky in her day cabin so the two of them could exchange sitreps. The Admiral had no further news as far as Halsey was concerned, but did communicate her disappointment in having learned that Colonel James Ackerson had been confirmed dead. Parangosky told Serin she could link up with the near Venezia and cross deck both Spenser and Muir to get them off her hands. If that wouldn't work and they became loose ends, however, the old woman stated plainly that she expected Serin would lose them another way. Upon questioning why she had evacuated Muir in the first place, Osman made the case that executing an unarmed civilian in front of her team wouldn't have been one of the best things she could do for their trust in her. After severing the connection she took her place on the bridge and gave permission to enter slipspace for Reynes. She asked Black-Box how long he expected the transit to take, to which he replied that his best estimation gave them around thirty-two hours. In order to keep Spenser away from the hangar bay full of Covenant weaponry when he came aboard, she told the A.I. to have him transferred via their docking ring when the time came. After announcing her intentions to pay their new passenger a visit in the meantime, Naomi offered to come along. Osman thanked her for the offer but insisted she could handle any trouble he might give her. She took multiple ladders down to the officer's accommodation deck where Tom was locked within a cabin and guarded by Mal. She went in to see the refugee, who was extremely suspcious of his rescuers and why they had been meeting with Covenant species. Osman was able to convince him they were merely exchanging bodies. She also reinforced that everything on the ship was classified and that was why he was quarantined. Muir was indignant at the way he was being treated and threw the seeming abandonment of New Lllanelli by Earth in her face, but she cooly informed him that Earth had lost billions when the Covenant attacked. After the cabin door shut behind her, she told Mal she didn't think he'd be a security risk. If he was, however, she also said she wouldn't hesitate to do what was necessary.

Reynes and Venezia
"Vasily Beloi"

- Serin Osman Once Kilo-Five arrived at Reynes, the ODSTs went to the surface to extract Spenser. An altercation with a group of Kig-Yar scavengers resulted in the scavengers' deaths. Osman's reaction to the spurt of violence was to ask if any typically Sangheili rifles were present on the scene that could be used to direct the blame for the killings elsewhere. In addition to this encouragement to make more of a mess in order to stir things up, as she put it, she requested that a couple of Jackal corpses be brought aboard the Port Stanley, as there was no telling when they might be able to make use of them. Serin met the returning marines in the hangar while they were unloading and, satisfied with their work, told them to place the bodies in the cryo store alongside Jiralhanae cadavers and body parts already frozen there. Their next stop was Venezia and the Monte Cassino in particular, so the captain let everyone know they should stand by to jump as soon as they had completed their necessary tasks. Her immediate concern was having a short chat with Spenser. Six hours later, they had dropped out of slipspace in the Orso system but the destroyer they were to meet was still five hours behind them. The UNSC Ariadne was still in trouble and Venezia had continued to refuse it any assistance. It would take about two hours for them to reach the ailing patrol ship at sublight speed, but before Osman could even plan their next course of action, the Ariadne exploded due to its reactor finally melting down.

By the time the Port Stanley was only ten thousand kilometers from Venezia, Osman could star at a viewscreen on the bridge and watch the Ardiane's drifting debris. Black-Box let her know when Spenser was ready to take his leave and at this she took her seat and opened a channel to the. She asked its XO, Commander Cerny, how long they planned to continue searching the debris field, which he guessed would take around another hour to do a complete job. Cerny offered to send a shuttle her way to retrieve Muir and Spenser, but under no circumstances was she going to allow that to happen, and so she told him she'd be sending one of her own his way. The XO asked Osman to stand by at that point, as Venezia Tower Control (TC) was reportedly making noise about the destroyer encroaching on the colony's territory. Osman scoffed at such a suggestion from what she considered an unapologetically rebel faction. While Cerny argued, Spenser entered the bridge alongside Phillips and Vaz to say goodbye to her. He teased her about how the power she would wield once she took over for Parangosky and she suggested that if Muir asked what they had been transporting, he could tell them man they were selling narcotics to the Unggoy. Vaz stayed behind on the bridge after Phillips and Spenser left and asked the captain if she planned on doing anything about what had happened to the Ariadne. She regretfully admitted they couldn't at the moment, as dealing with the colonies was currently Fleet Admiral Hood's pet project and because they had their own mission that took priority. As the waited for Devereaux to return from dropping off their former passengers, she settled into perusing an English transcript Phillips had prepared of the Sangheili communications they had intercepted from the Servants. She was jolted upright by a stern warning from Venezia TC broadcast for the Cassino. BB informed her that he told Dev to hang back at once and Osman had him signal the other UNSC ship to let it know they had their back. Before long, an ultra-heavy bolt of superheated plasma fired from a ground-based Type-38 Tyrant anti-aircraft cannon sailed passed the Cassino, which responded in kind with a missile of its own which destroyed the weapon. Following this, Osman made sure that Muir and Spenser were still taken by the ship. She had BB confirm nobody over there could hear her after signing off with Cerny. Osman was plainly enraged by Venezia's audacity and Mal offered to insert on the planet for reconnaissance once he, Vaz, and Naomi rejoined her on the bridge. She had no choice but to proceed to Sanghelios for the next stage of their mission at the moment, but vowed they would return when they could. Venezia had suddenly become her number two place which she was determined to screw over and she wasted no time drafting a contact report of the incident they'd witnessed to send to Parangosky.

Taking the Piety
"It's your call. If you think I'm going to get you all killed, then you tell me, and we just destroy Piety and sacrifice the Engineer."

- Serin Osman It was February and only a few weeks since the start of their mission by the time the team arrived in the Urs–Fied–Joori system for the next part of it. The Port Stanley, hidden, came to rest at a stationary position in Sanghelios space. Osman joined the ODSTs and Phillips in the hangar's maintenance area just as Mal was openly wondering how many Spartan-IIs there had been. Serin surprised them all by speaking frankly about the sordid histories of the Spartan-II and Spartan-III programs. She had no reservations about making them aware that she had been kidnapped as a child and subjected to various genetic and biochemical enhancements at age fourteen before her body began to reject further attempts to make her more deadly. The captain changed tack immediately after dropping this bombshell, letting her team know that BB had intercepted voice traffic from a small Jiralhanae transport, the Piety, that was inbound for Sanghelios. The Piety, crewed by at least six Brutes, was apparently not only transporting weapons for 'Telcam, but a Huragok as well. She informed them that their prowler would intercept the other craft in just eighty-two minutes and that she wanted to meet in ten in order to plan how they would take its valuable prize for themselves. Before she strode away, she told Mal to break out the dead Kig-Yar they had collected on Reynes. Port Stanley was five-hundred thousand kilometers off of Sanghelios when Mal, Vaz, and Phillips came onto the bridge where the others were already studying a holographic projection of the Piety. Osman concluded that they had two options. They could either board it via their own dropship or haul the enemy craft into the Stanley's hangar after disabling it with an EMP and attempt to crack it open there. Though securing the Engineer was the primary goal, Osman made clear that losing it would not be a wholly unacceptable outcome, as they could always just make sure Telcam's Jiralhanae were blamed and sow more dissent that way. When Mal asked why they UNSC didn't already have its own Huragok, she told him she knew of one that had been captured a couple of years ago and plumbed for valuable information that had been crucial to various developments before being lost. Osman was slightly worried about the prospect of a potential self-destruct of the Piety if they brought it aboard, but ultimately agreed that if they sealed the hangar's emergency bulkhead but leave the rear doors open to hard vacuum, then the damage to their ship from any explosions would be minimized. Fully aware that she was asking some of the team to put themselves in mortal danger, she made clear that if anyone had any objections, they could always just fire on the Brutes from a distance and call it a day. Her democratic appeal was met with no such reservations from the marines or the Spartan. Black-Box guided them through a visual demonstration of how the plan would unfold. Once the Piety was blindsided with a blast from their electromagnetic pulse cannon, they would need to move fast. Devereaux would maneuver the dropship onto the enemy transport's back and lock grapples onto her. The Port Stanley would be, in the meantime, be ready to receive the dropship with its attached Brute transport, which would fly right back into the hangar it launched from. One it was secured in the hangar, Naomi would breach it with Mal and Vaz as backup Satisfied with the plan, Osman removed Black-Box's data crystal chip from the command console. Though a fragment of the A.I. would remain to pilot the prowler, the rest of him would be tagging along with Naomi. Devereaux departed ten minutes later and all Osman could do was watch the operation through the HUDs of those involved overlaid on a viewscreen on the bridge. She had BB rearrange the order of the four of them in order to keep Devereaux's separate from the others and told her over their radio link that if the Piety managed to regain power and start dragging her away, she was to disconnect from it at once. Nothing like that happened, as once BB fired the pulse Lian had no trouble at all linking up with it and hanging on all the way back to the corvette.

A change in plans
"Margaret Parangosky"

- Serin Osman Soon enough, the six Jiralhanae within the Piety had been neutralized. Osman broke in over the radio when Vaz asked where Devereaux was in order to let them know she and their dropship were still attached to the top of the Brute transport and now waiting for its parking space to open up again. When the captain initially asked if they'd acquired a live Huragok, they hadn't, but Vaz found it hiding within a ventilation duct soon enough. Osman went straight for the hangar and descended the gantry ladder to the deck to see if for herself. Naomi cautioned her to stay bay, as the biomechanical Forerunner creation was still fitted with the explosive harness common among those Huragok that had been controlled by the Covenant. With help from BB, the Spartan was able to disable and remove it safely, finally allowing Osman to come closer. Serin congratulated everyone on a job well done and asked BB what they ought to with their new friend. In the A.I.'s opinion, it was crucial that they confine it somewhere where it would be unable to access his processes or any of the Stanley's critical systems. Taking possession of the Huragok pleased Osman greatly, and she could barely contain her excitement to share the find with Parangosky. She admitted that the prudent thing to do would be to get it back to Bravo-6 as soon as possible, but she also believed it may be of use to the mission at hand. Whatever the right decision was, she only knew that she needed to get in touch with her mentor before they did anything else. Before she left to establish a connection, she asked if there was anything onboard the Piety for it to eat.

A short while later, Osman found herself checking over the Piety as she had already done before to see if there was anything they could strip from it for their own use. Four tagged weapons that they had given to 'Telcam had already managed to spread to this group of Jiralhanae. Where the weapons went didn't matter to Osman, but she was interested in piecing together the supply route this find suggested. The comms on the Piety had been used to contact at least one Kig-Yar party within the Orso system, but the ship couldn't have come from that sector of space anytime soon, as it lacked a slipspace drive. Furthermore. BB got the impression that the Brutes and Kig-Yar in question hadn't been trading, as the Piety's flight path suggested it had recently been trying to avoid another ship. Osman planned to send the ship to resume its prior journey down to Sanghelios and asked Phillips if he thought the Servants were likely to do any sort of forensic analysis of the bodies within. He didn't think they would. Osman concluded that they would plant a single Kig-Yar corpse onboard and that they'd also give it an MA5B assault rifle, as even a cursory glance would show the Jiralhanae hadn't been killed by plasma weaponry. Assured that the plan was sound, she exited the cargo bay to breathe some air not befouled by the stench of death. Black-Box appeared and reminded her should she still wish to tell Parangosky about the Engineer, her next scheduled OPSNORMAL with the Admiral was in thirty minutes.

Right before the time to make the call came, Osman wandered into the wardroom galley following the smell of Jamaican coffee. There, she found Devereaux and the Huragok, evidently named Requires Adjustment. Adj had made modifications to the galley's coffee machine. Osman was impressed by the improvement but cautioned Dev not to let it try to mess with her neural implant. She hoped to have the Piety away before she talked to Parangosky, so Serin asked BB if he was finished nobbling its navigation computer so it would resume heading for its original destination and fabricating internal records to reflect an attack by Kig-Yar pirates. Osman sarcastically said she hoped nobody in Mdama would notice one of the Brutes had a broken neck but settled into her seat in her day cabin to watch the launch from there. Once she was finally speaking face-to-face with Admiral Parangosky, she first let her know they would just be making their second drop of weapons to 'Telcam soon but that tagged ordnance from the first had already made its way elsewhere. In her assessment, the Servants' insurrection was still only simmering but he thought it possible that the group may have acquired a warship and a few more competent shipmasters very recently. Parangosky announced that Fleet Admiral Terrence Hood would be traveling to Sanghelios himself within the next week, as he planned to meet with the Arbiter within his home state of Vadam as a gesture of peace and to convince him to reciprocate by attending a ceremony on Earth in remembrance of those killed in the final battle of the war. John-117, the Master Chief, would be at the top of the list of those honored. Parangosky suggested that Serin might want to be the one to tell Naomi he was lost. Osam asked if they were admitting that Spartans could die now, but Margaret assured her they were not, though the public knew refusing to do so was just a service courtesy. The Admiral's birthday was coming up in a few days and though the news about John saddened Serin, she wished her mentor a happy birthday and let on that she had a gift for her: the captured Huragok. She said she was committed to getting it into her hands as soon as they were able to get back to Earth. Parangosky was grateful and let Osman know she had something for her as well, as she believed they had finally located the place Halsey was hiding.

Osman's satisfaction with the news was plain to Mal and Vaz when she emerged from her day cabin and called for a meeting on the bridge in five minutes' time. Once everyone had gathered, she began by letting everyone decide whether she should give a fair bit of background regarding news she received from Sydney or simply plunge straight in. She was reassured that the crew would be able to keep up, so she went full steam ahead, noting that anyone was free to stop her at any point with questions. First, she informed them of the upcoming memorial service in Kenya. She gently broke the news to Naomi concerning the Master Chief being MIA but likely dead. Naomi asked if she knew anything about Fred-104, Kelly-087, or Linda-058, but Osman had nothing for her there. The captain then told her childhood comrade and everyone else that Dr. Halsey was also being being officially declared to have been killed on Reach. Moving briskly along, Serin announced that they would remained stationed near Sanghelios for the time being in order to keep an eye on Admiral Hood's visit to the planet. She made sure everyone was clear that no matter the outcome of his meeting with the Arbiter, it would not affect their current mission. She then suggested that once that business was concluded, they may be diverted to the former location of Onyx in the Zeta Doradus system. She explained what the artificial world had been and what had become of it and that while Onyx itself might be gone, evidence indicated there was still something there. She let slip that not only would it be advantageous to the UNSC to acquire any Forerunner technology they could get their hands, but that there may be personnel that needed rescuing. Devereaux asked who in particular they would be extracting, but at this Osman became uncharacteristically tight-lipped. Realizing that her reticence was obvious, she admitted she was holding some information back for now because it had personal implications for both she and Naomi and she wished to talk one-on-one with her before sharing it with the rest of the group. Dev communicated her appreciation for the captain's honesty and Osman reciprocated it by reiterating that she trusted each one of them and valued their assistance in her decision-making, which meant she wanted to be as transparent as possible. The meeting was adjourned and everyone but Naomi left the bridge. As a means of preparing her to learn the truth about Halsey eventually, Osman shared some of what she knew regarding Naomi's family. She explained how she had been replaced by a flash clone after being taken, and that this clone had died shortly thereafter, leaving them to grieve for her. To demonstrate the truth of this, Osman allowed her to read through Halsey's own journal. She suggested that if Naomi wished, she could read through classified files on her family when she was ready. It was a couple of hours before the Spartan made an appearance in the hangar following their talk.

The crown Jul
"Evan Phillips"

- Serin Osman Over the next twenty-four hours, the Port Stanley monitored traffic around Sanghelios and gathered intelligence. 'Telcam eventually contacted the ship spoke to Phillips, who then went to Captain Osman to confirm another appointment with the Bishop for a second weapons handoff. Figuring they would still have time to make it back before Hood arrived, Osman had the ship set off for New Llanelli once more. There, she chose to ride down to the surface this time to meet with 'Telcam in person once again. The Field Master had caught wind of Hood's upcoming visit and offered to kill him if that was something Osman wished for. She brushed aside the idea by saying that such an action would be of no benefit to either of them. While they were speaking, Naomi ambushed a Sangheili who was spying on the interaction from a short distance away. She managed to subdue him with assistance from Mal and Vaz and after the Servants' had departed with more tagged weapons Osman walked over to see what was going on. She told Naomi to continue to restrain the Elite while she made a call to Parongosky for direction. From Earth, the admiral encouraged her protégé to take the interloper prisoner. She rejoined the ODSTs and Spartan and relayed what she'd been told. She also gave the order to find their new captive's transport and to salvage what they could before destroying it.

On the way back to the Urs-Fied-Joori system, Phillips was tasked with attempting to speak with the Sangheili prisoner to find out who he was. By the time they returned to just off of Sanghelios, however, nothing had been learned that wasn't evident after going through the nav data on his ship. All Osman had been able to confirm was that he was from Mdama. Standing outside the Port Stanley's brig with Evan, she prodded him for his thoughts on whether or not they ought to notify the Bishop about nabbing him. He reasoned that the Sangheili's absence would likely be noticed eventually, which Osman of course had already concluded herself. Mal and Vaz joined the two of them to observe the captive through a one-way monitoring plate. After BB showed up visually, Captain Osman asked the A.I. if the Elite's armor could tell them anything. To this end, Black-Box recommended using Requires Adjustment to interrogate it. Given that the prisoner would like be less than cooperative, she summoned Naomi. The Spartan arrived bearing a humbler stun device and before long she and the two ODSTs were in the brig with a hostile. The Huragok was able to do what they wished thanks to their help, but Vaz took a hard uppercut blow from the Sangheili. Not wishing to take any chances, Osman ordered him to take a shot of chorotazine to prevent paralysis. She couldn't help but tease the professor with the idea of what might have happened if she'd allowed him to just go in an try to convince the Elite to let them inspect his harness and directed him to return to eavesdropping on local Sangheilli transmissions. After making sure Naomi was alright and confirming to Mal that they were still going to supervise Hood's diplomatic visit, she retired to her cabin with plans to brief her boss on the latest developments. Before doing so, however, she had BB comb through Admiral Hood's secure files so she'd be on an even footing when discussing his plans with Parangosky. The A.I. was happy to let the captain know that his fragment back at Bravo-6 had recently taken the liberty of framing Damien Hogarth for overspending in response to continual attempts to snoop in Osman's own files with an A.I. named Harriet. Before she could make the call to Parangosky, Phillips came to see her to tell her that he had positively ID'ed their guest by listening to the Servants' voice traffic. His name was Jul 'Mdama and he was known to 'Telcam, though clearly had been tailing the Field Master surreptitiously.

Truth and reconciliation
"She hijacked a vessel, she lied to Admiral Hood to get him to deploy Spartans to Onyx, she abducted a Spartan, and she did so with the sole intention of hiding there with the Spartans until the war was over. So we're going to Onyx to help secure the Dyson sphere, and to arrest the bitch on charges of aiding the enemy. For starters."

- Serin lets her feelings toward Halsey show after Naomi asks what she was doing on Onyx. After Osman had debriefed with her superior, she gathered Kilo-Five together to inform them that Hood had arranged for three of them to be permitted to accompany him on Sanghelios to meet with the Arbiter, which would be happening in just about sixteen hours. It was decided that in addition to Osman and Phillips, Vaz would tag along as well to offer some amount of protection. While she had everyone's attention, Serin also let them know that after concluding business there, their next destination was Zeta Doradus. She explained they they could now say for certain that what remained of Onyx was a Dyson sphere presently encased in a slipspace bubble that rendered its realspace diameter only fifteen centimeters. She said the UNSC was getting transmissions from it, though, and that it seemed likely that it could be brought back to their dimension and plundered for the technological wonders it held. Naomi asked if it might be John that was transmitting, but Osman only shook her head before finally confessing that Halsey was still alive and that it was she, Franklin Mendez, and a handful of Spartans that were the personnel trapped inside. Naomi was curious as to how they ended up there, which spurred a short rant from Osman that covered the doctor's theft of a, abduction of Spartan Kelly-087, and lying to Hood in order to divert other Spartans away from Earth when they had been needed there the most. She bluntly stated that they were going to arrest her for aiding the enemy. Naomi cautiously asked whether the captain knew Halsey's side of things, and Osman admitted she did not yet. Parangosky had told her that the doctor wasn't to know she was under arrest until the cuffs were already on her, so the matter of her most recent war crimes hadn't come up in the conversations had so far after reestablishing contact. Osman hammered home that despite her age and civilian status, she was to be considered extremely dangerous regardless and not to be underestimated. She said it was also of great importance that to the public, she would still be considered to have died on Reach. The plan was to hand off Jul 'Mdama to the right before going dirtside to get Halsey.

Fleet Admiral Hood arrived in the system aboard the. Osman and Phillips met him in the ship's crew room. Upon greeting the man, Osman steered him away from Phillips so they might have a word alone. She was pleased to learn that he was already well aware that Thel 'Vadam did not speak for all Sangheili and that there were a great many of his kind that thought peace with humans to be anathema. She also briefly brought up Venezia in order to see where he stood on recent events there, at which he expressed unease at the hardship that lay ahead of him with respect to the Outer Colonies. In the Iceni's shuttle bay, Vaz and Devereaux were waiting and ready to go when the rest of the shore party joined them. Dev piloted them down through the planet's atmosphere, flanked by an escort of the Arbiter's, to a discrete subterranean entrance. The gaping hole in the earth led to a tunnel that ended beneath Kolaar Mountain with a landing platform. The ODST, xenoanthropologist, and naval officers traversed a connected corridor until they found themselves in a small audience chamber and face-to-face with 'Vadam himself. Osman resigned herself to being a passive observer of the exchange that followed, in which the Arbiter and Hood agreed to the end of hostilities between their peoples, as far as it was within their power. As they were on their way back to the Iceni, Osman told Hood she thought he had pulled it off. He asked her if she knew about any Sangheili prisoners ONI may be holding, as he had agreed to release any in exchange for the return of any human captives the Arbiter's people had. Serin deftly dodged the question. A message from one of Thel's underlings was already waiting for them when they got back to the ship. It turned out that the Arbiter was interested in having Phillips return at his invitation for a tour of Sanghelios. Osman only said that they would discuss the proposal, turned down Hood's offer of drinks, and took her crewmen back to the Port Stanley.

Kicking in the Door
"Catherine Elizabeth Halsey, I have orders to detain you and take you to the nearest secure ONI facility on charges of committing acts likely to aid the enemy. You are now under military jurisdiction and do not have the right to an attorney. The maximum allowable period of detention before being formally charged or released does not apply. Come with me, please."

- Serin dispassionately recites the appropriate litany before Halsey is arrested. Once the team found itself near to where Onyx had used to orbit Zeta Doradus, it was only a matter of waiting while Requires Adjustment communicated with other Huragok inside the shield world in order to bring it out of slipspace. The captain joined the ODSTs and Naomi at a viewscreen while they watched for the reemergence of the impossibly-large object. She queried BB about docking procedure, to which he commented that an entrance should form within the shell of the sphere at wherever they approach it. When Devereaux asked about their plans for any valuable technology inside, Osman said that Parangosky had promised a briefing in which she would provide direction regarding it. She did agree, however, that at the very least they ought to secure another Huragok to be a companion and to Adj and so that he could be maintained. As soon as the enormous superstructure sprang back into visible reality, Serin donned a vacuum-rated helmet and made for their dropship along with the others. During the flight to the shield world, Dev mentioned Venezia and Osman confirmed she hadn't forgotten what it had done and still planned to screw it in return somehow. She went over the plan for arresting Halsey, saying that Parangosky wanted her in one piece and able to answer questions, but that they were all authorized to use whatever force necessary should she resist in any way. As the fateful meeting approached, Osman openly wondered whether the doctor would recognize her.

She didn't have to wait long for the answer to her question, as Catherine recognized Serin immediately, despite not having seen her since she was a teenager. Mendez also picked up on who she was and extended a friendly greeting, which she reciprocated. Fred, Kelly, and Linda were only slightly behind the other two in placing her face. Serin admitted it had been difficult purposefully leaving them in the dark about her situation for years. Leaving no time for any further pleasantries, she then calmly read Halsey the charges against her and explained she was to be detained without any of the civil liberties that would be due to subjects of civilian arrests. Vaz slipped a pair of microfilament cuffs on her and the two ODSTs marched her off. Osman only jogged to catch up with the trio within a passage a short time later and explained that they would be back for Mendez and the Spartans after she was secured aboard their ship. Halsey guessed that they'd be delivering her to Bravo-6, but Osman let her know that Parangosky would actually be leaving the planet's gravity well to come to her. The doctor asked why the admiral was coming down hard on her now, finally. All Serin could say in return was that she had been living on borrowed time for years and should have known her violations of the law and human decency would catch up to her eventually.

The Port Stanley maintained orbit around the massive shield world, now designated ONI Research Facility Trevelyan, for a few days following Halsey's arrest. Despite originally planning to hand Jul 'Mdama over to the Glamorgan, plans for the Sangheili prisoner changed with the circumstances so that he was instead taken to be held within Trevelyan. Osman oversaw his voluntary binding at the insistence of BB and escort by Naomi to the dropship personally. His total length of stay on her ship had been eight days. The survivors that had been with Halsey had all come aboard along with her, but on Osman's (and Parangosky's) orders they were forbidden from having any interaction with her. She would only remain onboard until the arrived to pick her up. Where it would take her was not shared with Mendez or the Spartans, but they were informed that their own next stop would be Sydney on Earth for debriefing. While they waited for the Compton-Hall, Serin invited Mendez into her day cabin to chat. Vaz paid the captain as visit while they were speaking there to ask permission to view a file related to Naomi's abduction and its effects on her family, as the Spartan had asked him to look over it for her. He dared to ask whether Serin would look at her own related file now, but she flatly said that she still would not.

Unshakable Conviction
"Margaret Parangosky"

- Serin Osman The memorial ceremony at Voi for those who gave their lives fighting the Covenant and those who pursued the enemy to the Ark in particular, was held on March 3. All of Kilo-Five was in attendance. Following the ceremony's conclusion, Osman made the case to Admiral Parangosky for Evan's insertion to Sanghelios to gather intelligence as the Arbiter's invited guest. She assured her mentor that if he became compromised in any way while spying for them, that Black-Box could administer a lethal dose of nerve agent to him at will. She also mentioned that she was still planning on following up on the Venezia situation. Parangosky specifically then asked Serin to keep an eye on the colony and to lend assistance to Mike Spenser, now reassigned there, should he request it. The admiral even went to far as to suggest that she wouldn't mind if an orchestrated Sangheili attack were to befall the planet.

Before she took her leave, Margaret let Serin know once more that though she hadn't yet talked to Halsey in person, she would very soon. Osman dared to ask if she carried any guilt herself for the Spartan-II program, to which the admiral admitted she did. She said she didn't regret it, but she always knew it had been wrong. She even told Osman she planned to admit to her role in the program when she testified to the UEG's Defense Committee. That would not happen, however, until she was convinced her subsequent resignation would not compromise security. After that, her role as CINCONI would fall to Serin. Parangosky notified her then that she would be promoted to rear admiral in the April list. She congratulated her protégé on the work she'd done so far with Kilo-Five and finally departed. Osman saluted her as she went. Almost immediately as soon as she was on her own, Chief Mendez approached her. The chief let her know that none of Blue Team's Spartan-IIs wished to access their classified files. The two parted amicably. Gathering her team, she directed everyone to their waiting transport. She asked Vaz if the memorial's focus on the Spartans had offended him as an ODST, but he said he was just glad the praise was at least going to NCOs and not just senior command.

The Port Stanley was waiting for them just beyond Earth's orbit, ready for a fast slip.

Mission on Sanghelios
After an explosion in Ontom, Sanghelios severed Kilo-Five's communication with BB's fragment and Phillips, Osman immediately ordered Kilo-Five to regroup aboard Port Stanley, which then made a slipspace jump to Sanghelios to recover him. Osman had Devereaux fly Tart-Cart to Ontom amid 'Telcam's assault on Vadam while herself coordinating the operation from Port Stanley. While initially failing to locate Phillips in the temple, Kilo-Five eventually recovered him from the Nes'alun keep in Acroli.

Meanwhile, the Fleet's new flagship,, turned the tide over Sanghelios as it decimated the Abiding Truth's forces. As the battle began to turn against the Abiding Truth, Admiral Parangosky ordered Kilo-Five to extract 'Telcam as he was necessary to maintain the imposed stalemate between the two Sangheili factions. With Osman aboard Port Stanley, Kilo-Five headed planetside aboard Tart-Cart and forced 'Telcam into the dropship. While Lord Hood and Infinity openly aided 'Vadam and defeated the attackers, with BB's help, Port Stanley posed as a Kig-Yar pirate ship. Disguised a Shipmistress named "Lahz", Osman and BB covertly destroyed some of 'Vadam's ships under Admiral Parangosky's orders, leaving the Arbiter with a Pyrrhic victory. After the battle, Osman rendezvoused with Tart-Cart and dropped 'Telcam off at New Llanelli for his safety.

During the battle, Osman learned that the Kig-Yar Skirmisher Sav Fel had stolen the Covenant battlecruiser Pious Inquisitor. Tracking down the ship became Kilo-Five's new priority in addition to their investigation on Venezia.

Venezian movement
After the operation on Sanghelios, Vaz and Naomi were inserted on Venezia disguised as UNSC deserters. Shortly after their arrival in New Tyne, they spotted Naomi's father and known Venezian terrorist Staffan Sentzke in the company of Sav Fel, the current possessor of Pious Inquisitor. Shortly thereafter, Osman pulled Naomi off the Venezian infiltration mission and substituted her with Mal as her family ties might compromise the mission.

In April 5, Osman was promoted to rear admiral and a small party was held aboard the Port Stanley in her honor by Kilo-Five.

One week later, when Vaz and Mal were not responding to Osman through their comm gear, she called Spenser and asked him to look for them. At BB's suggestion, she sent Requires Adjustment, Devereaux, and Naomi to Anchor 10 with Tart-Cart to retrieve a new dropship for Kilo-Five, having it immediately upgraded with the same capabilities as Tart-Cart. While at Anchor 10, they also retrieved a parcel containing ginger Parangosky had shipped to Osman for her slipspace-induced nausea. Meanwhile, Osman discovered that Mal and Vaz had been captured by the Venezian militia. Osman immediately tasked Naomi and Devereaux with the rescue mission. During the rescue mission, Osman provided tactical support from the Stanley. Devereaux piloted the Tart-Cart to rescue Vaz, while Naomi went after Mal with the new Pelican, entitled Bogof. The rescue mission was a success and Devereaux took Staffan Sentzke hostage.

They returned to Port Stanley where Sentzke was informed about the Spartan program and allowed to reunite with his daughter. Aboard the Stanley, Osman and Naomi attempted to convince Staffan to end his terrorism. Staffan agreed to hand over the Inquisitor in exchange for his daughter. However, Osman suggested to let Naomi decide if she wanted to return to her family or not, which Staffan reluctantly agreed to.

Pious Inquisitor
With Staffan's uneasy cooperation, Kilo-Five set out to retrieve the Inquisitor. However, the team soon found out that the ship had been boarded by a Kig-Yar crew, led by Shipmistress Chol Von, attempting to commandeer the ship for themselves. The Inquisitor's resident Huragok, Sometimes Sinks, was distrustful of the Kig-Yar and humans, put the ship in lockdown and only listened to Staffan. While Mal, Vaz, Naomi, and Staffan boarded the Inquisitor, Osman remained on the Port Stanley with the rest of Kilo-Five and Spenser, providing intel for her teammates aboard the Inquisitor. Staffan and BB worked with Sinks to take the ship out of lockdown. Attempting to keep diplomatic relations with the Kig-Yar, Osman had BB inform them that they were allowed to leave freely, but they refused the offer.

With Mal and Naomi pressing on the bridge, Chol Von set the ship to explode and escaped with her remaining crew. Kilo-Five escaped to their dropships and returned to Port Stanley, while Sentzke commandeered a Spirit dropship, intending to escape ONI captivity. Sentzke was not seen leaving the blast radius when the ship self-destructed and was assumed dead; unknown to Kilo-Five, he had actually survived, his Spirit having been outfitted with a miniature slipspace drive by Sometimes Sinks.

With Pious Inquisitor destroyed and the Venezian threat seemingly neutralized for the time being, Osman reported back to Parangosky and they discussed Osman's inheritance of the CINCONI's post and their future course of action with Dr. Halsey. Following this, Osman decided to read her own file, discovering that her origins were very unlike the idealized image of a happy family life she had previously imagined. She decided to visit her former teacher Alkmini Leandro in St. Malo on her birthworld of Cascade while the rest of the team were given a brief shore leave.

The Ferrets
"Serin Osman"

- Veta Lopis

A little less than two months later, on July 6, 2553, Rear Admiral Osman was briefly present on Gao, accompanying Blue Team in the Owl Silent Claw as they exfiltrated from the planet after Operation: JOVIAN WHISTLE. On the way off the planet, she announced the reassignment of Blue Team's three Gamma Company Spartan-IIIs and recruited Special Inspector Veta Lopis into ONI. At the time the head of ONI's Beta-5 Division, responsible for most of ONI's black operations, Osman subsequently oversaw the Ferret program and more specifically the team comprising Veta Lopis, Ash-G099, Olivia-G291 and Mark-G313. On October 14, 2553, Osman supervised a training exercise between Lopis' Ferret Team and Oscar Squad in Neos Atlantis' UNSC Recreational Facility 6055-NA-A. The exercise turned into a crisis when Lopis' team was targeted by Dark Moon Enterprises and reporter Spencer Hume was killed, although the Ferret Team was able to resolve the situation to Osman's satisfaction.

Leading ONI
By March 2555, Osman had risen to the rank of Admiral and had taken Parangosky's place as head of the Office of Naval Intelligence. After it was discovered that the active installations of the Halo Array were counting down to fire in several weeks, Osman convened in Bravo-6 with several high-ranking UNSC members and scientists concerning the crisis. It was proposed that a joint UNSC-Sangheili task force be sent to Installation 00, the most likely source of the countdown, in order to prevent galactic extinction. Osman vehemently spoke against involving the Sangheili in the operation, but was overruled by Terrence Hood. Afterwards, Osman awarded Captain Annabelle Richards with the Medal of Honor, after she declined a promotion, for her success at leading the task force at the Ark.

Requiem and Infinity
On July 25, 2557, she served on the UNSC Security Council committee that debriefed John-117 following the New Phoenix Incident. The Security Council decided to tell the general public that the incident was a Covenant attack stopped by the Master Chief. During the later stages of the Requiem Campaign, she was contacted by Captain Thomas Lasky, informing her about Doctor Halsey's abduction by the Promethean Knights. She had been recommended to either keep Halsey in confinement or have her executed, but instead chose neither. Questioning the doctor's loyalties, Osman followed Parangosky's advice and ordered Lasky to execute Doctor Halsey after years of reluctance.

On March 3, 2558, Osman was on the UNSC Security Council committee that debriefed Lasky and Palmer. She berated Lasky over Halsey's escape and the complete destruction of Requiem. Osman then questioned Palmer, who defended Lasky's actions to spare him of any ramifications from Osman.

Later in May 2558, after the UNSC High Command failed to remove a Kig-Yar pirate base on the planet Ven III, Osman had Sangheili mercenary Ayit 'Sevi hired to lure the Infinity to the base. On May 8, 2558, Admiral Osman spoke with Captain Lasky to discuss the threat of a mysterious bioweapon on Ven III. Osman tasked Infinity to dispatch a two-man Spartan team and capture the Sangheili, claiming he was an associate of Jul 'Mdama, in possession of the biological agent. After Infinity destroyed the base and captured the Sangheili, ONI operatives arrived at the planet in a prowler, seized the bioweapon, and led the unrestrained Sangheili aboard the prowler—acting out the orders of Admiral Osman. After the incident, Lasky was debriefed by Osman. Lasky noted that the debriefing went surprisingly well, despite the fact that Lasky had turned a covert operation into a battle. Lasky attempted to gain more information about the operation from Osman, but she told him to drop the subject. On September 15, 2558, Osman organized Operation: ATHENA, a mission in which a team—consisting of Spartans Palmer, Gabriel Thorne, Holly Tanaka, Doctor Henry Glassman, and 'Sevi—would infiltrate Breath of Annihilation and reveal the location of the Absolute Record once 'Mdama's fleet arrived at the location. Osman briefed three UNSC officers on the mission before she tasked Lasky with overseeing the operation.

The Created
In late October of 2558, Cortana, who had been restored within the Forerunner Domain and had come to believe that the Created were the true inheritors of the Mantle of Responsibility, began to unleash Guardians to enforce the Mantle among all the galaxy's species. Having anticipated her imminent assault on Earth, Black-Box acted swiftly to ensure that at the very least, Serin Osman and Fleet Admiral Terrence Hood would be able to get off-world. After he secured himself with the rest of the military AIs at HIGHCOM Facility Bravo-6, he informed Osman to collect a briefcase addressed from one Commander Spartan Rossbach and evacuate from Sydney. Osman followed his instructions and then proceeded to the top of the HIGHCOM tower with Lord Hood, where Orzel, a Spartan-IV, awaited them with a readily automated Prowler. Just before their Prowler jumped safely to slipstream space, Serin witnessed a Guardian disable the over Sydney and feared if the Plateau's engine core detonated when it hit the ground that the city would be destroyed.

After a series of random slipspace jumps, the Prowler arrived on an uncharted planet where a wooden retreat was well stocked for their long stay. After a few days of settling in the cabin with Orzel and Hood, Osman opened the briefcase which housed nine chips containing the secured HIGHCOM AIs, including the newborn Sankar AI and Black-Box. After activating Black-Box through her datapad, Osman learned that they were on Rossbach's World, a secluded planet discovered two years prior and named after BB's shell personality. After Black-Box revealed that he secured the other AIs before they had a chance to join the Created, Osman was left with a choice to make, whether to destroy the military AIs or not. In the following weeks, Serin stalled on making a decision about the AIs inside the briefcase. During one early morning, she took the briefcase with her on a jog through the nearby forest and soon pondered about taking the proper course of action. She then contemplated whether she should destroy the AIs to prevent them from disclosing any military secrets to the Created, decide to recruit them as Dr. Catherine Halsey had once done for her and the other Spartans, or speak with each of them and grant them the choice of joining Cortana.

Personality and traits
Due to Admiral Parangosky's long-time influence on her, Osman is virtually an extension of the former CINCONI's will; by indoctrinating Osman and arranging her to be the new head of ONI, Parangosky ensured that her legacy and policies would continue unchanged. Before her ascension to Parangosky's place, Osman still questioned the morality of some of the actions she and Kilo-Five routinely committed, such as actively working against the Arbiter's forces, although she never failed to follow Parangosky's orders. Years later, such concerns appear to have evaporated; for example, Osman coldly ordered the assassination of Dr. Halsey, though her lack of hesitation may also have to do with her antipathy toward the doctor, likewise passed on from Parangosky. After finally reviewing her file and discovering her tragic roots, Osman was forced to reconcile this information with her hatred of Dr. Halsey. Although she truly despised the woman, she could not deny that Halsey had taken her away from a terrible situation and given her a better life than she would have otherwise had, likely saving her from a terrible fate.

As CINCONI, Osman has also inherited her predecessor's intimidating reputation; Captain Lasky, for example, was visibly nervous when contacting her about Halsey. Osman rarely acknowledges her visitors; if Osman stands up upon a visitor's arrival, the gesture is considered a genuine show of respect. Osman has an odd relationship with Fleet Admiral Lord Terrence Hood; she recognizes that Hood is wiser and has more experience than her, but Osman worries that Hood may formulate solutions to problems that she could not solve. For this reason, Osman never openly questions Hood's involvement in ONI issues.

Osman experiences unusually strong symptoms of vertigo and nausea during slipspace transitions. While she was away on missions, Parangosky had crystallized ginger regularly shipped to her as a remedy. During high-stress periods of time, she also experiences recurring nightmares of her childhood abduction and early life as a Spartan-II trainee.

Trivia

 * As an admiral, Osman is the highest-ranking Spartan of any generation.
 * In the audiobooks for the Kilo-Five Trilogy, the narrator voices Osman with a Australian accent, reflecting her background at Bravo-6 in Sydney. She speaks with an American accent in Spartan Ops.
 * Çelik means "steel" in Turkish.

List of appearances

 * Halo: Glasslands
 * Halo: The Thursday War
 * ''Halo 4
 * Spartan Ops
 * Halo: Escalation
 * Halo: Mortal Dictata
 * Hunt the Truth
 * Halo: Hunters in the Dark
 * Halo: Last Light
 * Halo 5: Guardians
 * Limited Edition
 * Halo Mythos
 * Halo: Fractures
 * A Necessary Truth
 * Rossbach's World
 * Halo: Envoy
 * Halo: Retribution