Locus

"We're going hunting."

- Locus to his men in Reconciliation

Locus is a dangerous mercenary who first appears in S.O.S. and is seen listening in on Washington's distress call for help. His intentions were originally unknown, but it's revealed by Felix that he intends to kidnap the Reds and Blues for the Federal Army of Chorus and prevent anyone to help them escape the planet Chorus. Locus serves as the main antagonist of Season 11 and Season 12.

Overview
Confirmed to be a new character by writer Miles Luna in a tweet, Locus' overall concept could be considered to be a combination of several antagonists from the past. He's shown to speak little and is threatening like the Meta, is intellectual like the Director, has a cruel sense of humor like Omega, and is a sociopath like Sigma. However, he has great respect to those he believes deserve it. Like Felix, Locus is comparable to a popular mercenary, Deathstroke from DC Comics, as they are skilled mercenaries with respect for their targets.

When the planet Chorus went into a civil war between the New Republic and the Federal Army of Chorus, Locus joined the Federal Army and became a well known threat to those siding with the New Republic, such as Felix, a mercenary he seems to have a rivalry with. Upon learning that the Reds and Blues, which many believed to be some of the greatest military soldiers in the galaxy, crash landed on Chorus, he intended to kidnap them and have them use their skills for his superiors. Locus intends to complete his missions by any means necessary, including killing innocent bystanders or sacrificing his own men.

Hunting the Reds and Blues
In his first appearance, Locus discovers Washington's call for help after the Reds and Blues are left stranded on Chorus, but doesn't respond. Locus later arrives at the teams' location and begins spying on them, remarking the situation they're in as unfortunate before cloaking himself. Later on, Locus kills the pilot that dropped off Doc, Donut, and Lopez and reports in to 'Control', stating that his objective is complete and that he's returning to Crash Site Bravo.

Back at the crash site, Locus once again spies on the teams, but soon turns his sights on Felix. When the latter notices him, Locus activates his cloaking and returns to a control camp filled with white-clad soldiers. He gathers four of them back to Crash Site Bravo, where they proceed to attack the Blues. But when his men are killed by Tucker and Freckles, Locus attempts to shoot Wash in the head, but Felix appears and blocks the blow with a Hardlight Shield. Locus then shoots Felix in the leg and orders the Reds and Blues to come with him, believing that they are the 'real deal' after dealing with his men, but they refuse. After Locus threatens them, Wash orders Freckles to fire upon Locus, but the latter disappears before being hit.

Battle at Crash Site Bravo
Afterwards, Locus returns to the crash site, accompanied by many more Federal soldiers, and engages the group. During the battle, Locus uses a Sticky Detonator to destroy the Blue Team's tank, and later fires at a plasma grenade behind Donut, knocking the latter unconscious. As the Reds and Blues retaliate, Locus fires several blasts from his Railgun towards Wash and Sarge, incapacitating them. As New Republic reinforcements arrive, Locus attempts to stop Felix, Simmons, Grif, Tucker, and Caboose from escaping into the caves, but fails when Wash has Freckles seal off the entrance by collapsing the tunnel's roof.

However, he manages to incapacitate Washington afterwards. After the battle, Locus communicates with a superior (soon revealed to be Carolina), whose voice is distorted, and informs her about a crate he recovered. He then suggests that he execute a captured Sarge, Donut, and Washington, but Carolina challenges him, asking if he feels threatened by them. When he responds negatively, Carolina reaffirms for him to obey orders before stating that she would see him soon.

Fighting the New Republic
Several weeks later, Locus is seen at a Federal Army outpost killing a disguised Cunningham. After ordering his fellow Feds to sound the alarm, Locus looks around the room for other infilitrators, unaware that Tucker is cloaked in the room with him. He soon leaves after hearing an explosion and discovers Felix, Tucker, and Palomo at the facility.

Personality
Locus is portrayed as a quiet and cold individual who is shown to be serious about his objectives. According to Felix, "[Locus] is so far off the deep end he prefers to go by the name of his armor instead of the name he was born with." Locus also seems to enjoy his occupation and is quite sadistic, as he treats his attack on the Reds and Blues with amusement and makes a morbid joke when he kills the pilot. He also remorselessly sent a team of four soldiers to their deaths just to test the Reds and Blues.

Despite this, he's shown to have respect to those he considers the "real deal," like the Reds and Blues. Locus is also cunning, as he's shown to outsmart several characters. Along with this, Locus is quite perceptive, such as in Lost But Not Forgotten, he clearly becomes suspicious of his "superior" when the latter orders him to not execute the captured Reds and Blues. However, his cruelty, dark tone, and skills show that he should be considered a deadly threat to everyone.

Weaponry
Locus has been shown to have skills with several weapons. His skills with the sniper rifle are superb, as he would have killed Washington if Felix didn't interfere and snipes a plasma grenade near Donut to injure him. In Fire, Locus is shown to use the Railgun very effectively, as he quickly incapacitates Washington and Sarge with it. Along with this, Locus has been seen to use a shotgun, pistol, SAW, and sticky grenades in battle.

Combat
Locus appears to be a deadly combatant. He's responsible for incapacitating most members of the Reds and Blues during the battle at the crash site and is shown to be skilled in close range combat, as he executes three rebel soldiers as he approaches the remaining members of the Blood Gulch teams. Along with this, he uses cloaking effectively, as he was not only able to spy on the Reds and Blues, but also escape the teams without a trace using the enhancement in several instances. It also seems many within the New Republic fear him, as when Felix mentions Locus to 'Headquarters', the operator is clearly scared.

Intelligence
Locus is shown to be very calculative, allowing him to make the best choices that specifically benefit himself. For example, Locus stops a pilot to prevent others of learning the location of the crash site and instead of immediately attacking the Reds and Blues, he observes them from a distance and wisely sends in a team of soldiers as cannon fodder in Neighborhood Watch in order for him to know about the Reds' and Blues' skills. Locus is also in command of a large group of Federal Army soldiers and leads a successful attack at the crash site, resulting with the remaining Blood Gulch soldiers to retreat.

Kills
With no remorse, Locus has killed the Dropship Pilot using a shotgun and pistol. It's also implied he killed other individuals prior to Worst Laid Plans, as an unknown corpse is seen near the Fueling Station. In Fire, he kills several New Republic soldiers when the teams attempt to escape. In Hit and Run, he manages to kill a distracted Cunningham via a point-blank shotgun blast.

Trivia

 * Locus' armor in Halo 4 consists of a Locus helmet, Infiltrator torso, Engineer left and right shoulders, and Outer-Plated arms and legs.
 * Locus appears at Crash Site Bravo (and speaks for the first time) in the tenth episode of Season 11, similar to the tradition where Tex makes a bold appearance in the tenth episode of several seasons. Along with this, he is shown to have cloaking, an armor enhancement that Tex also possessed.
 * Before his name was revealed, many fans of the series called Locus 3G, which stood for Green Gray Guy. This relates with his armor color, as sage is a shade of green and steel is a shade of gray.
 * It's revealed Locus works for a higher command that he refers to as Control in Worst Laid Plans (later identified as the Federal Army) and is in command of many Federal Army soldiers in Reconciliation.
 * It is revealed in Ready…Aim… that Locus doesn't use his real name, but rather a name based on his armor (specifically his helmet). This is similar to Freelancers using their assigned state name rather than their real names.
 * It's implied that Locus went insane or has a mental illness by Felix. If true, then evidence suggests he suffers from antisocial personality disorder (ASPD), which is a pervasive pattern of disregard for, or violation of, the rights of others. This is similar to Locus' lack of empathy for others in the series.
 * Locus might be a reference to Darth Vader from the Star Wars franchise as both characters have dark voices, dark colored armor, forsook their birth name, are incredibly skilled fighters and command numerous white armored soldiers. Additionally, Locus can be compared to Boba Fett given both are skilled mercenaries fighting for the antagonists of their respective franchises.
 * Locus' voice helmet filter is noticeably different from other characters, as it is less compressed and more deep and acoustic sounding, adding to his menacing persona.