The Weapon

"The Weapon" (AI Serial Number: CTN 0453-0) is the moniker of an artificial intelligence. She was created as an exact copy of the AI Cortana, designed to enter an installation to imitate Cortana and lock her down for retrieval. With the growing threat of the Banished and the Harbinger, the Weapon became the Master Chief's permanent new AI companion, replacing Cortana.

Creation
In October 2559, Dr. Catherine Halsey dispatched Blue Team on Operation: WOLFE to retrieve three cryobins and a lockbox from a cryovault beneath the ruins of CASTLE Base. Halsey insisted that what they were retrieving was the key to stopping Cortana, although she warned John-117 that while it would not be easy, it was the only option that they had. The contents of the bins, the remaining cloned brains from Halsey's creation of Cortana, were used by her to create the Weapon for the mission of entering an installation to imitate Cortana and lock her down for retrieval. Halsey created the Weapon to be an exact copy of Cortana with any information that could compromise the Weapon removed by Halsey. As she neared her completion, Dr. Halsey introduced the Weapon to the Master Chief, and he was briefed on the plan to capture Cortana and deliver her to the for termination. Upon the Weapon's successful deployment, her deletion routine would be executed.

Defeating Cortana
Shortly after the Infinity arrived at Installation 07, she was ambushed by a Banished boarding party force led personally by Atriox. As the ship quickly became overrun, Captain Thomas Lasky ordered for the Weapon to be deployed immediately. Meanwhile, the Master Chief stayed behind on the Infinity to hold off the Banished as Lasky was escorted to a dropship. Once on the Halo, the Weapon was able to lock down Cortana in the Silent Auditorium. Cortana was destroyed, though not through means apparent to the Weapon. In reality, Cortana had willingly destroyed herself and damaged the ring in order to prevent Atriox from using it against humanity. She also deactivated the Weapon's deletion routine so that she could accompany John-117 during the struggles that lay ahead. As a result, the Weapon was left active within the ring's foundation, believing that the Master Chief was due to come back for her.

Teaming with the Master Chief
Six months after the defeat of Cortana, the Master Chief was revived and returned for the Weapon, whom he was surprised to see was still functioning. Not knowing how or why her deletion was averted, she was recovered and accompanied him across Zeta Halo, which was now controlled by the Banished following the crippling of the Infinity. Recovering the framework that the Weapon had used to lock down Cortana, the two witnessed echoes of Cortana's life scattered across Zeta Halo's systems.

The Weapon helped the Master Chief as he traveled across Halo, destroying a mining drill after he took out the cooling pipes,, disabling one of the Reformation spires and collecting data on the Reformation, and helping him to destroy three Banished AA guns.

However, in order to help the Master Chief access the Command Spire, the Weapon was forced to interface with four Forerunner beacons in order to override a lockdown on the Command Spire. Throughout her hacking, the Weapon was observed by another presence and it was only on the fourth beacon that she realized that it was actually the Harbinger. The Weapon realized that it was a trap with the Harbinger trying to break the deadlock on starting the Spires by combining the Weapon's routines with the Monitor's. The Master Chief suggested stopping and creating a stalemate, but the Weapon warned him that the Harbinger is close and that she would eventually find a way. With no other choice, the Master Chief allowed the Weapon to proceed, but he discreetly activated a deletion protocol for the AI just in case. When nothing happened to her, the Weapon suggested that she was just being paranoid and the Master Chief dodged her question about what he was saying while activating her deletion protocol.

Later, while interfacing with Halo in the Nexus, the Weapon was trapped in the system by the Harbinger. The Weapon begged the Master Chief for help, but, worrying that the AI had been compromised, he went through the authentication to manually delete the Weapon instead. However, the Weapon managed to break free of the Harbinger's clutches and override the deletion protocol. The Weapon was livid that the Master Chief was willing to turn on her so quickly rather than trust in her to break free herself while he was furious that she had stopped him and put them all at risk. The Weapon confirmed that the Reformation has begun, but reveals that she had managed to steal Pyre's encephalon from the Harbinger, reminding the Master Chief that she was an infiltration program. The Master Chief continued to argue that she broke protocol, causing the Weapon to demand what was wrong with him as she was only trying to help them and it was worth the risk before activating a gravity lift.

The Weapon continued to accompany the Master Chief, but her tone shifted to outright dejection and sarcasm towards the Chief, even telling the pilot what the Master Chief had done to her. The Master Chief and the Weapon made their way to the top of the Command Spire, defeating Adjutant Resolution once again. Once three attacking Banished Phantoms had been destroyed, the Weapon interfaced with the Command Spire, continuing to treat the Master Chief with sarcasm and dismay over his earlier actions. The Weapon, lacking her usual enthusiasm, shut down the Spire network and successfully stopped the Reformation before demanding answers from him, pointing out that she had waited for him for six months, done everything that he'd asked and while she was supposed to be deleted, he was the reason that she was still here and he could never have accomplished all that he had done on Halo without her. The Weapon demanded to know why he can't trust her like she had trusted him, and he brought up Cortana, but the Weapon told the Master Chief that Cortana was dead and all that was left of her were echoes that will be gone too sooner or later. Echo 216 arrived with the news that all of the Spires were shutting down and the Weapon informed the two men that while the Master Chief was ready for pickup, she was staying in the Command Spire. The argument was interrupted by Jega 'Rdomnai attacking the pilot in the cockpit and flying off with him after the Master Chief couldn't get into the Pelican to rescue him. The Weapon warned the Master Chief that the pilot didn't stand a chance against a Spartan Killer, and he ordered the Weapon to track them and open a portal to somewhere close by. The Weapon argued against this, warning that they could die trying as it was hard to lock down the coordinates, but he had her do it anyways and they departed through a portal in pursuit of 'Rdomnai and the pilot.

Facing the truth
The Weapon teleported to the two to the Repository under the Banished base, but they passed through a data cluster in the process, causing the Chief to witness more of Cortana's memories. Hacking into a terminal, the Weapon played a challenging message from Escharum to the Chief and retrieved the coordinates of the Banished base from the message. As they continued, the two witnessed Cortana destroying Sydney as an example to Lord Hood when the UNSC refused to surrender and her having Leonidas destroy Laconia Station due to the threat that the Spartan IVs there posed to her. After witnessing Cortana destroying Doisac as an example to Atriox, the Weapon finally realized that she was actually a copy of Cortana herself, which the Master Chief confirmed, explaining that it was the only way to infiltrate the installation's systems and lock down Cortana. The Master Chief explained that the Weapon had all of the same systems and routines as Cortana, but Halsey had scrubbed any information that could have compromised the AI. "You're her. If we'd never met," stated the Master Chief. Horrified by Cortana's actions and the idea that she could end up the same way, the Weapon restored her deletion protocols and asked the Master Chief to delete her, but to promise to rescue the pilot as the Master Chief was all that he had left. The Master Chief instead downloaded the Weapon back into his armor so that they could do it together, admitting that while he didn't trust her, he wanted to.

Rescuing the pilot
Upon arrival at the House of Reckoning, the Weapon helped to guide the Master Chief through the Banished base towards the pilot's location, expressing surprise and confusion at Escharum's transmissions throughout their journey. Upon reaching the pilot, the Weapon attempted to free him, but they were interrupted by the arrival of Escharum for a final battle between the old War Chief and the Master Chief with the Weapon remaining in the system to work on getting the pilot out at the same time. When Escharum surrounded himself with an energy shield by using the relays in the room, the Weapon warned the Master Chief that any injuries to Escharum would hurt the pilot and helped him to destroy the relays and Escharum's shield. Once Escharum was completely vulnerable, the Weapon shouted encouragement at the Master Chief until he won the fight. After Escharum was defeated, the Weapon was able to free the pilot and the three of them witnessed Escharum's death from his wounds in the Master Chief's arms. Although the pilot believed it to be over since the Banished leader was dead, the Master Chief warned that there would be consequences while the Weapon stated that the intricacies of any action were complex, confusing the pilot. With the Harbinger at the Silent Auditorium, they needed to move because whatever she was planning was worse than Escharum and the Banished. The three then departed the House of Reckoning to stop the Harbinger and her plans.

Returning to the Silent Auditorium
As Echo 216 approached the Silent Auditorium, the Weapon realized that it was the location where she had locked down Cortana and where Cortana had died. Fighting their way through the structure, the two witnessed Cortana's memories of her facing off with Atriox after she had been locked down, although, unlike the previous memories that the two had seen, these memories seemed to be more purposeful, as if Cortana had purposefully left them to be found. From these memories, they learned that Atriox had pressured Cortana to surrender control of the ring to him and that the Weapon's deletion had been prevented by Cortana herself after Cortana realized that she had unwittingly set in motion a chain of events, which would put all life in the Milky Way in mortal danger. Cortana knew that the Weapon would be John's sole option for stopping the plans of the Banished, as she would no longer be able to. After a final confrontation with Atriox, Cortana sacrificed herself to destroy the part of the ring containing the Silent Auditorium, apparently killing the Banished leader.

After finally reaching the Harbinger, the Weapon monitored the transmissions to another location and attempted to deduce their contents while helping the Master Chief to stop the Harbinger. As time went on, the Weapon was unexpectedly aided in her work by an unknown entity within the Silent Auditorium's systems. When the Harbinger died, she sent off a final transmission to an unknown location, one that was sent too fast for the Weapon to deduce more than the fact that it was to something old. Afterwards, the two witnessed a final message recorded for the Master Chief by Cortana, in which she apologized for her actions and hoped that the two may learn from her mistakes and become better for them. Cortana also relayed to the Master Chief that she felt that the Weapon had a lot of potential.

With the Silent Auditorium collapsing around them, the Master Chief and the Weapon fled up a gravity lift that suddenly appeared and returned to the surface. Much to her surprise, the Weapon learned that they had been gone for three days and the Master Chief and the Weapon were extracted by Echo 216. Preparing to continue their fight with the Banished, the Weapon asked for the pilot's name and he finally introduced himself as Fernando Esparza and asked what he should call the Weapon. Rather than pick himself, the Master Chief offered to let the Weapon choose her own name - much like Halsey had done for Cortana. The Weapon informed her companions that she had the perfect name for herself and they flew off together in the Pelican.

Personality and traits
Unlike Cortana, the Weapon has a sunny and naive personality due to her young age and lack of experience, with a tendency to be optimistic even about things that seem grim. Due to Halsey apparently limiting the information that the Weapon has access to, she lacks basic knowledge on things such as what the Banished and even the ex-Covenant species such as the Hunters are. However, she shares some traits with Cortana such as often snapping her fingers when performing an action and, due to possessing the same routines and systems as Cortana, she possesses Cortana's skill in hacking into alien systems and retrieving or sabotaging things. The Weapon sometimes does this with enough of a dramatic pause that the Master Chief asks her if something's wrong before she completes the task. However, after the Master Chief tries to delete her, the Weapon is deeply upset as he was supposed to protect her and they were supposed to be a team. As a result, she takes on a more dejected and sarcastic tone while dealing with him. While shutting down the Spire network, the Weapon loses all of the exuberance that she had previously showed, simply stating that it had worked and that no there was not a problem before simply counting down and snapping her fingers, the exact opposite of when she would purposefully put in a dramatic pause before completing one of her tasks.

After discovering her true origin, the Weapon is horrified because of the terrible things that Cortana, who is essentially her, has done and she tries to delete herself. However, the Chief stops her, stating that while he does not trust her, he wants to, recognizing the differences between Cortana and her copy. Cortana even jokes that the Weapon has a lot of potential and that she makes a great replacement as the Master Chief's AI companion.

Along with being used when she completes a task, the Weapon's snapping of her fingers also appears to be something of an unconscious motion done when she's thinking about something, as seen when the Weapon is trying to figure out what the Master Chief isn't telling her and the Weapon is absently snapping her fingers. Snapping her fingers while doing something is likely a trait that the Weapon had inherited from Cortana herself.

Trivia

 * The Master Chief's deletion code for the Weapon is "RED FLAG 034 SAMUEL." Operation: RED FLAG is the mission to the Covenant homeworld High Charity that the Master Chief and Cortana were supposed to embark upon when they first met, while Samuel-034 was his best friend before Sam died in the Battle of Chi Ceti in 2525.
 * In Halo Infinite, the Weapon first transfers into the data crystal chip by touching it in the same way that Cortana did in Halo 3 before transferring into other systems by the Master Chief touching them like Cortana did in Halo 2, albeit with the Master Chief first manifesting a hologram of her above his hand.
 * In Halo 4, Cortana briefly predicts the future partnership of the Master Chief and the Weapon at the end of the level Composer, telling the Master Chief that "they'll pair you with another AI. Maybe even another Cortana model if Halsey lets them. It won't be me, you know that, right?" In her final message to the Master Chief, Cortana jokingly echoes this statement to him.

List of appearances

 * Halo Infinite