Feet first into hell!
Sarah Palmer was born on Luna on 13 April 2527, while her parents, despite living so close to Earth, were highly against the UNSC, she would later join the UNSC Marine Corps. She would move up in the ranks until she would join the ODST Special Forces. She would eventually serve 12 tours on 8 world as an ODST, and was considered by ONI to be a great asset due to her physical prowess and innate leadership.
Somewhere before October 2552 she gained command of her own ODST squad which was deployed to extract Admiral Kovalic. While her squad was scattered, her pod landed very close to the Admiral and she immediately came to his aid. The Admiral was under attack by a Jiralhanae Chieftain who wielded a Gravity Hammer. Palmer swiftly incapacitated the Jiralhanae and led Kovalic to a nearby Warthog where the Admiral told Sarah that he was carrying a highly valuable AI. She then used a Frag grenade to send the Warthog flying towards the recovering Jiralhanae, crushing him. The approaching Covenant forces where stunned long enough for Sarah and the Admiral to get in the Warthog and flee to safety. However, this was not before a single Needle round was fired in her upper chest.
After nearly 3 months of recovery about the Lockhart medical station, she was approached by the SPARTAN-III Jun-A266. Jun, together with Musa-096 had set up the SPARTAN-IV Program, and Sarah was supposed to be one of their first SPARTANs.
The SPARTAN-IV Program was the first SPARTAN program since the original project to use consenting adults, as commissioned by the ONI commander Admiral Margaret Parangosky. After Sarah had been briefed on the Program, she underwent the necessary SPARTAN-IV augmentation procedures. After she and some fellow SPARTANs had recovered from their augmentations, they were put through an obstacle course to see if they could sprint to a red button under fire, outnumbered 10 to 1, and without their Mjolnir Armor. As Sarah rushed the course to get to the button, she left her fellow SPARTANs behind, who were all hit by the stun rounds. While happy with her success, Jun and Musa quickly told her that being a SPARTAN was not about personal glory, and to work as a cohesive team.
After some more rounds of training, the SPARTAN team was led to the UNSC Infinity to show where they would be stationed. They were given a tour by Commander Thomas Lasky and Jun. While their tour was taking place, a band of Insurrectionists disguised as engineers infiltrated the vessel, kidnapped Captain Andrew Del Rio, and disconnected Aine, the ship's AI, from the bridge console. This team of Insurrectionists was led by Ilsa Zane, one of the original SPARTAN-IVs which were designed to not need MJOLNIR armour; they would be able to achieve the same feats as a person wearing the armour.
While Ilsa and her team had taken control of the ship, Sarah made her way to the armory with Thomas Lasky where she put on her Scout variant MJOLNIR armour. In an attempt to stop the SPARTAN by depressurising the Deck, but was unsuccessful as the SPARTANs were able to put on their armour in time. Together with the other SPARTANs, Sarah was able to fight Ilsa and push her into the void of space. While Ilsa was rescued by other Insurrectionists and brought to safety, the Infinity was once again under the control of the UNSC.
Battle against the ancient enemy
After the end of the Human-Covenant war, Sarah Palmer fought the Covenant Remnant on Draetheus V. She was given instructions to not only defeat the Remnant presence, but also to find and kill the Remnant's leader, Merg Vol. The entire Battle of Draetheus V was very bloody on both sides, with over 60% of the human forces killed, and the majority of the Remnant's forces. The fighting started when this Rogue Covenant Fleet ignored a ceasefire agreement between the Covenant Empire and the UNSC and attacked UNSC forces on Draetheus V's moon X50. The fighting stopped after Sarah successfully found and killed Merg Vol, with the help of Edward Davis who died on X50.
After Sarah was extracted and brought aboard the Infinity, she was promoted to the rank of Commander and given the mission to locate the remaining Halo rings to set up research bases. On Installation 03's research station Ivanoff, a science team was vaporised by a Forerunner artefact which led the Inifinty to Requiem. Here she was deployed to protect the Infinity against the Covenant Remnant and Promethean forces. While on their way in a Pelican which carried her and her fireteam, the Pelican was shot down and they were rescued by SPARTAN-II John-117. John had been on Requiem for some time, and had begun to understand that the Forerunner Didact was planning to escape Requiem and fight humanity. It was Captain Del Rio who was very much against John, and his only plan was to get the Infinity out of Requiem and signal Earth. Sarah then took control of Gypsy Company and was sent out to destroy the gravity well which kept the Infinity locked. Eventually, with the help of John-117, they succeeded and the Infinity could now flee from Requiem.
Once again back at the Infinity's bridge, Sarah Palmer observed how John's companion AI Cortana showed signs of rampancy. Andrew Del Rio saw this as a threat to the ship, and ordered Thomas Lasky to destroy of the faulty AI. After John-117 intervened and took Cortana for himself, Andrew Del Rio ordered Sarah Palmer to arrest John, in which she hesitated. While John was sent off in a fully-equipped Pelican by Thomas, she remained on the bridge. In was not until after the first defeat of the Didact above New Phoenix that she saw John-117 again, and she witnessed him having his MJOLNIR armour removed.
After Andrew Del Rio was relieved from command of the UNSC Infinity, Commander Sarah Palmer effectively became second-in-command behind Captain Thomas Lasky. Thomas may have chosen her due to her leadership and military knowledge, as well as her being the overall Commander of the SPARTAN-IV Program aboard the Infinity. Six months after the Didact's attack on New Phoenix, Infinity was to return to Requiem to clear out the Covenant Remnant and Prometheans and set up research bases.
While the Second Battle of Requiem was underway, Sarah mostly stayed behind on the Infinity to oversee and organise the many SPARTAN-IVs which were employed. After Fireteam Crimson had located a Forerunner artefact, it was brought aboard the Infinity were Dr. Henry Glassman studied it. After Henry touched the artefact however, he was teleported to Requiem and brought before Jul 'Mdama, the Covenant Remnant leader. As Thomas Lasky needed to know about the artefact, he brought Dr. Catherine Halsey aboard. Sarah showed outright hostility towards her, and viewed her as nothing but a war criminal. After a quick examination by Catherine, she told Thomas and Sarah that the artefact was in fact communicating with the Infinity's Forerunner engines, and some Forerunner tech on the surface of Requiem.
After Fireteam Majestic was sent to retrieve a package, they were attacked by a large Covenant Remnant force, which was overseen by Jul 'Madama and his second-in-command Gek 'Lhar. After Jul remarked that "they had made enough of a show of attempting to retrieve the package", the Covenant Remnant retreated and the package was brought aboard the Infinity. When this package was investigated by Catherine, she remarked that it looked remarkably like an AI matrix. While she was further investigating the artefact, Catherine was in constant communication with Jul 'Madama though her data pad. When Catherine muttered the word "Librarian", Sarah became suspicious and snatched the datapad from her. This led to Thomas sending her to the brig, where Catherine was accompanied by Roland.
Sometime afterwards, several Promethean Knights appeared aboard the Infinity, who were after Catherine. After attempting to steer the Infinity further away from Requiem, Roland remarked that they were tethered to the planet through the Forerunner artefact. Palmer expressed confusion, as slipspace isn't physical. Halsey remarked that there's still much they don't know about it. Palmer cut her off, criticising her for failing to fix this. After the Knights appeared in the bridge, one of them took hold of Catherine and teleported her away.
After Thomas Lasky was given orders to find and kill Catherine Halsey, Sarah Palmer happily volunteered for the job. Even though Thomas Lasky did not like the plan, he eventually let Sarah go. But while Sarah made her way toward Requiem, Thomas contacted Fireteam Majestic and told them to take Catherine into custody, not kill them. When Sarah made contact with Majestic and finally found Catherine, each responded to the orders they had been given, which resulted in Sarah Palmer shooting Catherine in her shoulder, but not mortally wounding her. Angrily explaining to Majestic that Catherine was nothing but a war criminal, sentenced to death, SPARTAN Gabriel Thorne showed her the piece of the Janus Key what Catherine had thrown to him.
While this angered Sarah immensely, they had far bigger problems. The Infinity was still tethered to Requiem, but Jul 'Mdama had set Requiem on a course toward the neighbouring star. Palmer worked with Majestic to take out one artefact while Crimson went after the other. Once their mission was complete, both Fireteams quickly made for Infinity and the vessel barely made it to slipspace as Requiem's collision caused the star to go supernova. As the crew rejoiced, Sarah later criticised Thomas for trying to thwart her. Thomas defended that he sent Majestic to rescue Catherine, not stop her, but she failed to see the difference. They then enter the lab where Glassman was examining the Janus Key. He determined that without the other half it is useless.
After the entire Requiem campaign, Sarah remained on board of the Infinity and trained in the War Games simulator. After one of these training sessions, she was told by Thomas that they were requested for a debriefing at HIGHCOM Facility Bravo-6. After Thomas Lasky explained what happened at Requiem, Sarah covered for him by saying that it was her fault for missing the shot on Catherine, not mentioning Thomas' part in the matter. After the briefing, Lord Terrence Hood tells her about an escalation in Jiralhanae raiding parties against the Sangheili throughout joint-occupational zones. He tells her that a meeting between the Jiralhanae elder Lydus, the Swords of Sanghelios leader Thel 'Vadam was to be supervised by a SPARTAN force on Eealen IV. While the negotiations are underway, they are attacked by the Covenant Remnant however, and Sarah orders them all to take shelter in a nearby plasma refinement facility.
While keeping the delegates inside, several fireteams are sent out to fight the Remnant's forces. Sarah destroys a Lich by sending a helmet full of grenades into its gravity lift. After the nearby Remnant forces are defeated, she finds a Sangheili with a UNSC data pad. On this data pad is all the information about the UNSC presence, containing profiles of every human on the planet. While other SPARTAN fireteams had secured a landing zone, Sarah, together with the delegates, made their way to safety. Once there, she grieves for the sacrifices her fellow SPARTANs had to make to secure their safe passage.
While aboard the Infinity, Roland gives them his assessment on what he was able to discover about a ship that was launched from the coordinates of a gas giant called Oth Lodon, in a Jiralhanae controlled system that is relatively close to Ealen IV. Hood decides it is time to tell them why it is his fault for James Cutter going missing. He explains that he was unable to retrieve a log buoy that the UNSC Spirit of Fire left at Arcadia before it entered slipspace, because he engaged the Covenant rather than try to retrieve the buoy stealthily. Sarah and Fireteam Majestic are then dispatched to search for the Spirit of Fire. However, they find a Covenant Space station instead, and bear witness to the Infinity being pierced by the station’s glassing beam. Palmer then led Fireteam Majestic into capturing the station, holding all the Insurrectionists who orchestrated the attack on the peace talks, before turning the glassing cannon on Vata 'Gajat's ship, destroying it.