The 1st Legion, also known as the First Legion, functioned as an elite stormtrooper legion within the Galactic Empire's military forces. This particular legion operated under the direct command of Sith Lord Darth Vader and gained notoriety throughout the galaxy for its close ties to Galactic Emperor Sheev Palpatine's right hand. Its members were hand-picked from the ranks of the equally famous 501st Legion, another stormtrooper legion that served directly under Vader. Stormtroopers of the 1st Legion who failed to meet Vader's stringent standards were either reassigned back to the 501st or summarily executed for their shortcomings. Kimmund, an officer within the First Legion, held the position of fourth commander within his particular unit, his predecessors having faced either demotion or death at the hands of the Dark Lord of the Sith.
Before the Galactic Civil War erupted, the First Legion was deployed to the planet Batuu alongside the forces led by Grand Admiral Thrawn. Their shared objective led them into conflict with the Grysks, a warlike people originating from the Unknown Regions. During their time alongside Thrawn, the First Legion engaged the Grysks in numerous battles, the first of which occurred on Batuu when Kimmund's troopers infiltrated a Grysk long-range heavy freighter and captured several Grysk warriors. However, the prisoners they brought aboard the Chimaera—an Imperial I-class Star Destroyer serving as Thrawn's flagship—attempted to seize the First Legion's transport, the Darkhawk, resulting in a battle from which Kimmund emerged alive thanks to the intervention of Thrawn's personal bodyguard, the Noghri assassin Rukh.
Following the unsuccessful prisonbreak, the First Legion participated in the Battle of Mokivj, where Darth Vader personally led the ground assault. During this engagement, Kimmund's troops successfully rescued the majority of the Force-sensitive Chiss girls who had been kidnapped by the Grysks. Thrawn and Vader, determined to recover all of the captives, tracked the Grysks who had escaped from Mokivj through hyperspace, leading to another confrontation in which the First Legion successfully freed the remaining Chiss children. The First Legion also provided support to the 501st Legion's Blizzard Force during the Battle of Hoth, where 1st and 501st Legion cold weather assault stormtroopers breached Echo Base under Vader's leadership.
The First Legion served as the personal stormtroopers of Darth Vader during the Galactic Empire's reign. These men and women were known for their association with the right hand of Emperor Palpatine, and the legion's troopers took pride in their standing within the Stormtrooper Corps. When Rukh dismissed the First Legion as "unknowns," Commander Kimmund countered the Noghri assassin's remark, citing the legion's reputation as proof of their fame. Grand Admiral Thrawn also held these soldiers in high regard, considering their actions against the Grysks to be exemplary.
The First Legion drew its members from the ranks of the 501st Legion, another renowned Imperial Military unit that also served directly under Vader. The 501st's history stretched back to before the formation of the Empire, when it was a clone trooper legion under Jedi General Anakin Skywalker during the Clone Wars. First Legion officers also originated from within the 501st, but those who failed to meet Vader's expectations, like Commander Kimmund's predecessors, were either demoted and sent back to the 501st or executed by the Dark Lord of the Sith. Kimmund believed that his only chance of survival was to ensure that his troops remained disciplined and obedient, given Vader's command style.
Besides Vader and Kimmund, the 1st Legion's officer corps included Sergeants Aksind, Drav, and Viq. As a legion within the Imperial Army, the 1st Legion could be divided into smaller formations. Kimmund led his own unit within the 1st Legion, which included a squad. The 1st Legion also utilized a modified freighter called the Darkhawk, while Vader employed a personal Lambda shuttle. During the Battle of Hoth, 1st Legion stormtroopers served as cold weather assault stormtroopers.
Sith Lord Darth Vader established the 1st Legion before the Galactic Civil War outbreak between the Empire and the Alliance to Restore the Republic. Following the Battle of Atollon, the Emperor sensed a disturbance in the Force emanating from the planet Batuu in the Outer Rim Territories of the galaxy. Vader and Grand Admiral Thrawn were dispatched to investigate, with Commander Kimmund accompanying Vader along with a contingent from the First Legion. They journeyed to Batuu aboard Thrawn's flagship, the Imperial I-class Star Destroyer Chimaera. The Star Destroyer was accompanied by the Sith's private Lambda-class T-4a shuttle and the First Legion's transport, the Darkhawk—a repurposed Clone Wars era Separatist starship.
During the journey to Batuu, tensions arose between Vader's legion and the crew of the Chimaera, particularly between Kimmund's unit and Thrawn's bodyguard Rukh. The Noghri warrior frequently boarded the First Legion's vessel unannounced, prompting trooper Sampa to install intrusion alarms on the ship's hatches to deter Rukh. Despite these precautions, Rukh still managed to infiltrate the Darkhawk, reaching the electronics shop this time. Using trooper Jid's helmet to trigger the alarm, he alerted the First Legion and was promptly escorted off the ship by Sergeant Drav and trooper Morrtic. Annoyed by Rukh's actions, Kimmund feared that the next security breach would result in either the Noghri's death or his own at the hands of the Sith Lord.
Upon reaching Batuu, Vader and Thrawn went to the surface, leaving their subordinates on the Chimaera. Soon after, a group of Grysk freighters arrived, and Kimmund's forces attacked the largest one after Thrawn refused to reveal the Chimaera's location to the enemy. Thrawn explained that the Grysks, a warlike sentient species from the Unknown Regions, posed a threat to both the Chiss Ascendancy and the Galactic Empire. While Vader and Thrawn confronted the Grysks' Darshi mercenaries, the First Legion deployed to the freighter via the Darkhawk. After a squadron of TIE/d "Defender" Multi-Role Starfighters led by Vult Skerris disabled the Grysk vessel's hyperdrive, the First Legion boarded the freighter and attempted to secure it and its contents for the Empire. Kimmund personally oversaw the effort to capture the cargo hold, following Vader's instructions to keep the cargo intact, but the Grysks detonated explosives, destroying both the cargo and themselves.
Although they failed to secure the cargo hold, Kimmund's men managed to stun some Grysks before they could complete their suicide mission. On Thrawn's orders, the First Legion transferred the prisoners to the Chimaera, where Thrawn intended to interrogate them. They were confined to personal quarters typically used by TIE fighter pilots, prompting Kimmund and Sergeant Aksind to remain aboard the Darkhawk with its pilot Tephan, feeling uneasy about leaving their ship unguarded with the prisoners nearby. When the Grysks escaped from their makeshift prison, they attempted to flee the Chimaera by stealing the First Legion's transport. A brief but intense skirmish ensued between the Grysks and Kimmund's companions, resulting in Aksind's death despite Rukh's timely assistance. Most of the aliens were killed in the fighting, but Kimmund and Rukh managed to recapture four of them.
Vader was displeased because he and Thrawn had allowed the Grysks to escape from their prison so they could steal a ship, all of which had been equipped with homing beacons that would lead the Chimaera to the enemy's secret headquarters. Kimmund, unaware of his superiors' plan, inadvertently thwarted it by preventing the aliens' escape. Kimmund believed he would have been executed had the Grand Admiral not defended him. The Grysks' decision to steal a Clone Wars era vessel like the Darkhawk led Thrawn to conclude that their base was an old Separatist droid factory on the planet Mokivj.
Upon the Chimaera's arrival at Mokivj, Thrawn requested to lead the ground assault personally using Vader's stormtroopers. However, the Dark Lord denied Thrawn's request and insisted that he remain with the command ship while Vader led the First Legion to the planet's surface. They successfully infiltrated the factory, where Vader created a diversion while Kimmund, Sergeant Viq, and trooper Elebe searched for the prisoners they were tasked with rescuing. Kimmund's stormtroopers killed the Grysks guarding the prisoners, but the Commander was surprised to discover that the captives were young Force-sensitive girls—three of whom were kept in hibernation chambers—of Thrawn's species, the Chiss. After taking the children into their custody, Kimmund and his troopers proceeded to the factory's courtyard, clearing it of enemy units to rendezvous with the Darkhawk. Aboard the Chimaera, Senior Lieutenant Lomar informed the Grand Admiral that the First Legion had succeeded in their mission and would return to the flagship with the rescued prisoners within the hour.
Upon the return of Kimmund's unit to the Chimaera, Vader informed the Commander that a small number of prisoners remained with the Grysks, who had escaped into hyperspace before Thrawn's Defenders could intercept them. At Thrawn's request, Vader used the Force to track the Grysks through hyperspace, believing that the Sith Lord's powers would lead them to the location of the Grysks' main forces and, consequently, the remaining prisoners.
Having tracked the enemy's lair to a star system, the First Legion planned to ambush the Grysk ship using the Darkhawk while the Chimaera attacked the main warships. Vader chose to support the First Legion by piloting one of the TIE Defenders, believing that his presence was not necessary for Commander Kimmund and the stormtroopers to carry out a breach and rescue operation. The trap was successful; with Vader disabling the engines, the First Legion boarded the Grysk vessel. Aided by Rukh's tracking abilities, Kimmund's unit began searching for the remaining Chiss captives, while two troopers guarded the Darkhawk. Although a few troopers died during the mission and Jid was left behind after being struck by a Grysk lightning gun, the First Legion ultimately succeeded in rescuing more Chiss from the Grysks.
As the Galactic Civil War intensified between the Empire and the Alliance to Restore the Republic, Darth Vader's Death Squadron was tasked with locating the Alliance High Command's base. Using Project Swarm, the Empire located Echo Base on the ice planet Hoth, and deployed its ground forces after arriving and the rebels activated their deflector shield generator. Darth Vader deployed the 501st's elite Blizzard Force, under the command of General Maximilian Veers. Blizzard Force's units were supported by the First Legion in the critical Battle of Hoth, which resulted in a major Imperial victory. Vader led 501st and 1st Legion snowtroopers into Echo Base.
Timothy Zahn created the 1st Legion for the 2018 novel Thrawn: Alliances. The English copy of "The Battle of Hoth and the Second Death Star" by De Agostini identified the 1st Legion as such, having previously written it out as First Legion when translated. Zahn mentioned in an interview that he initially wanted to include the 501st Legion as Vader's personal force of stormtroopers, as it was in Star Wars Legends. However, the Lucasfilm Story Group rejected the idea, stating that Vader would not have wanted to be closely associated with a unit that had been commanded by Anakin Skywalker during the Clone Wars. Nevertheless, Vader would still select his stormtroopers from within the 501st's ranks when recruiting for the First Legion due to the 501st's expert troops.
The First Legion's status as Vader's personal legion during the Galactic Empire contradicted the 2015 novel Battlefront: Twilight Company, where Everi Chalis referred to the 501st as Vader's personal legion. When asked about this discrepancy, Matt Martin of the Story Group suggested that either Chalis was mistaken or that the situation may have changed by the time of Battlefront. While the nickname "Vader's Fist" was attributed to the 501st in Star Wars Legends, The Odyssey of Star Wars: An Epic Poem applies it to the First Legion. However, Star Wars Helmet Collection and Star Wars: Battles that Changed the Galaxy also applied it to the 501st in canon. While Helmet Collection was released before The Odyssey of Star Wars, Battles that Changed the Galaxy was released afterward.