From Halopedia, the Halo wiki
Halo: Initiation is a three-part comic book series published by Dark Horse Comics. It acts as the origin story for Commander Sarah Palmer and is presented as a lead-in to Halo: Spartan Assault, which also stars Palmer. The series follows her career from her time as an Orbital Drop Shock Trooper to the leader of the SPARTAN-IVs aboard the UNSC Infinity.
A hardcover edition was released on January 21, 2014.
In January 2553, Commander Musa-096, a former SPARTAN-II, has arranged an audience with several admirals in HIGHCOM Facility Bravo-6. Despite reprehending the morality of the SPARTAN-II Program, Musa stresses the importance of the Spartans in the Covenant War and argues that they are still necessary, revealing that he has created a new generation of the supersoldiers. Three months earlier, in October 2552, a group of ODSTs, including Sarah Palmer, are deployed on a planet under Covenant attack. On the surface, Admiral Kovalic, protecting an important AI, is heading to an extraction point, but his Warthog is attacked by a Jiralhanae Chieftain. Palmer's drop pod lands nearby and she defends Kovalic from the Chieftain and other Covenant forces converging on their position. Even though she is wounded by a Needler shard, Palmer eventually kills the Chieftain and saves the admiral. Three months later, while still recovering in a UNSC medical facility, Palmer is visited by Jun-A266, who invites her to join the SPARTAN-IV Program.
A group of Insurrectionists have stolen plans to the UNSC Infinity. While some stand in disbelief, others feel it will be used to control the colonies; the leader, Ilsa Zane, plans to take the ship for the Insurrectionists instead. Meanwhile, Sarah Palmer undergoes the augmentation procedures to become a SPARTAN-IV. Later, during a training exercise against several Marines, she rushes ahead of her Spartan-IV teammates, who are disabled in the process, to accomplish the objective. Jun-A266 and Musa-096 berate her for this, with the latter emphasizing the importance of Spartans working as a team. Later, while the new SPARTAN-IVs are given a tour of Infinity by Thomas Lasky, the Insurrectionists make their way aboard the ship disguised as a construction crew. They take Captain Del Rio hostage and make their way to the bridge, taking control of the ship and hold the crew hostage. After realizing that the ship's AI, Aine, has been shut down, Palmer decides to take the initiative and outfits herself with MJOLNIR armor, picking the Scout variant from the armor bay's limited selection of suits.
While the Spartan-IVs prepare to fend off the attackers, Jun explains Ilsa Zane's background: she is the only survivor of a secret, prototypical phase of the SPARTAN-IV program. Although her physical augmentations are superior to those of the mainline Spartan-IVs, they also made her mentally unstable, resulting in her defection. On the bridge, the Insurrectionists are attempting to gain full control of the Infinity. As they detect the approaching Spartan-IVs, Zane activates S-deck's decompression system, ejecting several of the Spartans into space, with Thomas Lasky and Jun being saved by Palmer and Davis. Lasky contacts Captain Del Rio, while Palmer and Davis make their way for the Infinity bridge along the exterior hull of the ship. Zane sends a group of her henchmen to eliminate the rest of the Spartans, but Lasky manages to close a blast door between them. Meanwhile, Palmer and Davis storm the bridge, with Palmer facing off Zane in hand-to-hand combat while Davis takes on the rest of the insurgents. During the duel, Del Rio and the bridge crew enter the bridge and reactivate Aine, who opens the bridge's airlock. Palmer finally knocks Zane out, venting her into space. Later, an unconscious Zane is recovered by a prowler and wakes up to recognize an unknown individual. The narrative returns to Musa addressing the Admiralty. He states that the Spartans are to thank for exposing Admiral Mattius Drake and his rebel movement, the New Colonial Alliance, as well as saving the Infinity, and boldly declares the Spartans as an independent branch.