Leonidas

Leonidas was a "smart" AI formerly in command of the Spartan-IV training station. He also spoke with a slight accent, possibly meant to be Greek.

Creation
Leonidas was commissioned when the SPARTAN-IV program officially began. He was created using the mind of a man who died during the augmentation process. He was completed in the year 2553.

Administration of the Spartan training station
Leonidas was installed on the Spartan-IV training station at some point after the second class of Spartan IVs completed training there. His purpose was to ensure the day to day functions of the station worked well and he assisted Jun in the administration of the Spartan Branch and training.

Created conflict
After joining Cortana's AI faction known as the Created in October of 2558, Leonidas persuaded Jun to get some rest, who had stayed awake for multiple days after Cortana's uprising. Leonidas maintained the station, running it as if nothing had happened. He held complete control over outbound communications, and had gone dark under Jun's orders. When asked about Jun's condition, he referred to it as "indisposed".

Leonidas was unable to detect Alpha-Nine's Condor as it approached the station, yet didn't show any sign of surprise. He explained to Buck that everything was fine and that he had shut down all communication with the outside in response to the Cortana event. When Buck boarded the station, Leonidas appeared to him and, upon Buck's request, arranged for Buck to be able to speak to Michael Crespo. . Leonidas offered to upload a path to Crespo on Buck's HUD if Buck were to grant him access to Buck's navigational systems. Leonidas was unable to do this as Buck had locked down his armor's systems, and refused to allow him access. Unbeknownst to him, Vergil was currently shifting through the station's systems.

Leonidas eventually discovered Vergil's presence in the station's systems and cut him off from Buck's comms, who had entered the command center. Leonidas refused to show Buck to Jun, and began to openly show disdain towards Buck. After Buck further insisted that he needed to see Jun, Leonidas told Buck that he should return to his Condor, threatening that if Buck persisted, the consequences would be severe, if not fatal. Leonidas told Buck that if he wished to do things the easy way, he'd stand down and join Mickey in the brig. Buck did not comply, and in response, Leonidas declared station-wide that Buck had gone AWOL and that STOLEN GAUNTLET was in effect. Leonidas, ordered Buck's termination if he did not cooperate with arrest. The Spartans, who had been in the room with Buck, immediately pulled their weapons on him. Buck attempted to explain to them that Leonidas had gone rogue, only for Leonidas to respond that by resisting arrest, Buck was putting his fellow Spartans in harm's way. Leonidas vented all the air out of the room, suffocating the three Spartans, after Buck had started to get them to question Jun's absence. Leonidas demanded that Buck stop as the Spartan punched his way into Jun's office. Leonidas told Buck that if he did not surrender, he would open every single one of the station's airlocks and kill everyone on board on the count of three. As Leonidas counted down, Vergil shut down the power to many of the station's components, effectively blocking Leonidas from accessing its systems. Leonidas attempted to reason with Buck, but was cut off when Buck removed his data chip from the terminal.

Buck held off on destroying Leonidas' data chip for a while, before reasoning that keeping him active was too great a risk and grinding it to splinters under his boot. Despite this, Leonidas had stored fragments of himself in the armor of Dutch and Gretchen.

Cassidy III
When Alpha-Nine arrived on Cassidy III, Leonidas informed the Created of the location of Cassidy III. Vergil eventually learned of Leonidas' continued existence and cut off his ability to communicate, but by then the message had already been sent. Leonidas then spoke to Alpha-Nine, informing them of their impending doom, after Vergil had removed him from Dutch and Gretchen's armor and put him in a tablet. After a Guardian arrived, Alpha-Nine and the remaining members of the Front agreed to surrender to the Created and submit to Cortana's rule. Leonidas then contacted the Guardian and ended its destructive rampage. Leonidas was then brought to and placed on a durance node, that the Guardian deployed, by Buck. As the durance node was returning to the Guardian, the tablet that Leonidas was on was finally obliterated by a blast from Romeo's Gauss Rifle.

Destruction
What was left of Leonidas later made contact with Cortana and reported on the status of the station. Cortana had Leonidas destroy both the station and himself in order to remove the possible threat that the young Spartans posed to her.

Trivia

 * This AI was named after the Spartan King of the same name.

List of appearances

 * Halo: Bad Blood
 * Halo Infinite