Sigma (Mega Man X)

Sigma’s True Form as the Sigma Virus

Sigma, formerly referred to as "Commander Sigma", is the primary antagonist of the Mega Man X series. He serves as the final boss in all mainline games in the series except Mega Man X8 where he is the penultimate boss in Normal and Hard mode. Once the noble leader of the Maverick Hunters, Sigma fell into insanity and turned Maverick himself, becoming the leader of all haywire Reploids and waging war on humanity.

Sigma was considered Dr. Cain's masterpiece and the finest of the Reploids, and was the first leader of the Maverick Hunters; peace-keeping Reploids who defend humans against their renegade counterparts known as Mavericks. Although he was once honorable, Sigma unexpectedly goes Maverick at the beginning of Mega Man X and rebels against humankind. He defects to the Mavericks and assumes the role of their leader. Under Sigma's command, the Mavericks grow into a legion dedicated to the extermination of the human race. Sigma instigates many of the destructive Maverick Wars, with the Maverick Hunters existing to crush Sigma and his minions.

Although he has been destroyed countless times, Sigma's programming always survives and builds himself a new form, ready to menace the world once again. It is implied that he grows more insidious and vengeful with each transformation, with each successive plan becoming more and more desperate and aggressive. His primary enemies are X, Zero, and more recently, Axl.

As the former leader of the Maverick Hunters, Sigma was originally the most advanced Reploid of his time. Dr. Cain implanted the latest circuitry designs into Sigma, which were theoretically supposed to prevent him from going Maverick. He was placed in charge of the 17th Elite Unit of the Maverick Hunters, and led them to victory multiple times.

One day, the Maverick Hunters received reports of an overwhelmingly powerful "Red Maverick" that has destroyed an entire squadron of Hunters. While investigating, Sigma, along with his unit, tracked it down to an abandoned laboratory. Sigma then left to confront it alone and personally deal with it, in order to prevent other Reploids' deaths at the hands of the Maverick. It is here that Sigma encountered Zero, the last product of Dr. Wily. Zero, having suffered a programming flaw from his creation, was uncontrollable, unleashing wanton destruction wherever he went. Sigma was beaten badly by the maddened Zero, but managed to smash the energy crystal in Zero's helmet. The fight, due to taking place in close proximity to Zero's capsule, which was leaking trace amounts of the Maverick Virus, and the damage they already sustained in the battle, transferred the Maverick Virus directly into Sigma and Zero, infecting them. Zero lost consciousness, and Sigma limped away from the battle, ordering his men to take the body of Zero back for study. The virus had different effects on them: Although the virus corrected the flawed programming in Zero, it began to mutate and adapt to Sigma's own programming, eventually fusing entirely with his mind to form the Sigma Virus, which allowed him to manipulate and control Reploids, bending them to his will. After this, he began to feel that humanity was keeping Reploid potential down, and decided to revolt against humanity.

Sigma's advanced circuitry seems to do its job, as he seemingly remains stable for months after the lab incident. He gradually succumbs to the virus inside of him and grows more volatile. Without warning, he leads a mass revolt among the Reploids. Many Maverick Hunters follow Sigma out of loyalty, leaving Zero, who by this time was reformed and had become a powerful Maverick Hunter, in charge of the organization. Mega Man X, the last creation of Dr. Light and the base model for every Reploid, decides to join Zero as thanks for saving his life. X and Zero battle through the Maverick regime, and it is X who finally destroys Sigma, who laments X's decision for siding with humanity, feeling that Reploids would have prospered without humanity holding them back. But, though his physical body is scrapped, Sigma's "soul" survives. After the end credits roll, Sigma's face appears on a blue monitor and warns X that he will be back.

Just as he promised he would, Sigma returns and assumes leadership of his Maverick forces. He gains a new body with the help of the X-Hunters, a trio of vengeful Mavericks who worship him, and becomes "Neo Sigma". He also oversees the "Unification" plot, which focuses on capturing and re-assembling the remains of Zero, whom he plans to reprogram to kill X. But, since X managed to recover all of Zero's remains from the X-Hunters, Sigma was forced to make a copy of Zero's body that was not unlike Zero's Black Zero form; however, Zero arrives and destroys it completely before it could battle with X. Sigma then announces that he "knows Zero's secret", and that he's destined to serve him. It's unknown what exactly this secret is, but the dialogue suggests that it has something to do with Zero being created by Dr. Wily, and the possible origins of the Maverick Virus as Sigma calls him "the last of the Doctor's creations". Sigma attacks in his latest form, armed with clawed knuckles, but X thwarts his plans and destroys him again. This marks the first time Sigma's viral form is seen, as the final boss of the game. Zero is then restored to his rightful place in the Maverick Hunters, and is given command of his own Special 0 Unit. 

Sigma uses a hacker named Techno to hack into the Mother Computer of the Maverick Hunter base. Noticeably more confident than previous times, Sigma taunts X after he is beaten the first time and even calls his defeat at the end of Normal Mode merely a retreat. It is only when he is defeated on Hard Mode that he seems to succumb to X. However, he implies in the ending that he will return as long as not only Mavericks still exist, but also as long as humanity retains evil minds.

Sigma resumes his threat when he infects the Reploid scientist Dr. Doppler, who has developed a revolutionary new anti-virus to repel Sigma's influence. Prior to his reemergence, Sigma's bodies after they were destroyed were presumed to have been used for scrap. Sigma uses him to stage a revolt in Doppler Town, a Utopian city established on the principles of peace. Once Doppler is unmasked as a pawn, Sigma emerges in a heavily-armored form, "Kaiser Sigma". After his defeat for the third time, The Sigma Virus itself appears in the form of a wire-frame head, which is identical to its appearance in Mega Man X2, and threatens to possess X's body to replace its own. After chasing X through the flaming wreckage of the base, Sigma finally corners him. If Zero did not end up critically wounded at any point during the game, which would have forced him to leave the war to X as he was repaired, Zero appears and utilizes the anti-Virus created by Doppler to erase Sigma for the time being. If Zero did end up critically wounded, including the method by which X receives the Z-Saber, Doppler uses the anti-Virus and sacrifices himself to destroy Sigma's programming. 

In Mega Man Xtreme 2, Sigma appears in Extreme Mode after the defeat of Berkana or Gareth, where it's revealed he was behind the Erasure incident. In a rare instance, he's pleased that X defeated Berkana, claiming her greed went too far.

Sigma was thought to be suppressed forever after receiving the anti-virus created by Doppler, but he still manages to return. In the introduction of the game, Sigma, assuming a Grim Reaper-like appearance, acts as a double-agent between the Mavericks and Repliforce, a benevolent squadron of Reploids who assist the Maverick Hunters. Sigma's true motive is to conspire against Repliforce and turn it into a rogue enemy. He stages the bombing of the airborne metropolis Sky Lagoon, which plummets to the ground in the opening of the game.

With in-fighting between the Hunters and Repliforce threatening to destroy them both, Sigma increases his influence over the paranoid General of Repliforce. The General, an outspoken advocate of Reploid independence, loses all faith in peace and prepares a satellite laser attack on all humans, which is Sigma's real intention. Fortunately, X and Zero storm the space weapon and stop the General before he can turn its sights on Earth. In the end, Sigma is revealed as the true mastermind and battles X/Zero himself, armed with a new body and a scythe with a beam blade. Despite his defeat at X/Zero's hands, he succeeds in part by destroying Repliforce. In order to ensure both sides of the war were manipulated, he also had one of his agents, Double, infiltrate the ranks of the Maverick Hunters, and also seduced Magma Dragoon with the concept of power and a chance to fight X/Zero in exchange for instigating the war. He also had Cyber Peacock and Split Mushroom fight against X/Zero to test their power and capabilities. Eventually, he had Double fight X when he infiltrated the Final Weapon, and also ordered him to kill some members of the 17th Unit of the Maverick Hunters as their presence risked compromising Sigma's plans.

It is some time before Sigma resurfaces again. During his absence, Sigma traced Zero's origins to Dr. Wily, and hatches a plot to unlock Zero's "true" power - the Zero Virus - inside him. Sigma also adapts his programming to completely overwhelm the anti-virus; the Sigma Virus quickly begins spreading everywhere, turning peaceful machines and Maverick Hunters alike into violent servants of Sigma. The Maverick leader also enlists the help of a Reploid bounty hunter named Dynamo to crash the orbiting space colony Eurasia into the Earth, as well as to hinder the Hunters' plans of stopping the collision.

Sigma's ultimate goal is to mix his own viral code, which is spread across Earth, with Eurasia's virus to form the original Zero Virus, intending to make Zero "remember" who he is and revert to his original, intended programming. He fails in this endeavor, and both X and Zero defeat Sigma in his new bodies, Psycho Sigma and the gargantuan Final Sigma W.

In the aftermath of the battle, Zero's severed torso lies dormant on the floor. X picks Zero up and tries to get him to respond. The remains of Sigma's head lying nearby suddenly become active and fire an energy laser directly at X and Zero, hitting both of them in the chest. As Zero's body falls from X's grasp, he manages to fire one last blast from his Z-Buster and finishes Sigma. X is critically wounded in the battle, both from the battle itself and Sigma's final attack, but he is eventually repaired and returned to the Hunters.

Three weeks pass as the human population moves underground to survive the devastation and pollution left by Sigma's last attack. Sigma himself is quickly resurrected by a renegade Reploid scientist, Gate, who was angry at the scientific community for rejecting his advanced Reploid designs. Gate becomes a Maverick after coming into contact with the Zero's DNA in Eurasia remains, a piece of rubble that contains signatures of the Zero Virus. He then uncovers Sigma's remains, and proceeds to rebuild him. However, due to the stress of spreading the Sigma Virus during Mega Man X5's "Colony Incident", Sigma's programming is damaged beyond what Gate can repair, and he is reduced to a half-conscious and barely-functioning wreck of his former self. Gate's work on Sigma's new body is unfinished by the time X or Zero confronts him at the end of the game. Although it seems as though Gate rebuilt Sigma merely as a backup plan to further his own goals, Sigma is quick to finish him off after X or Zero finally defeat Gate in battle, stating: "Oh please, I did not die, nor did I need your help. Now get lost!"

After X or Zero defeat his first form, he emerges as a gigantic unfinished body with a skeletal appearance named Hell Sigma.

Along with his final lines before being destroyed, this is the only instance in Mega Man X6 in which Sigma speaks coherently. He seems to remember little more than his rage toward X and Zero and speaks in a garbled voice.

Sigma reappears yet again, under the alias of "The Professor", to manipulate the Maverick hunting organization known as Red Alert. His plan was to use a mysterious young Reploid named Axl to copy the D.N.A. signatures of X and Zero and implant them into destructive war machines. The plan fails when Axl flees Red Alert and seeks asylum with the Maverick Hunters.

This prompts Sigma to find a way to bring Axl back into the Red Alert group. He secretly infected the eight Red Alert generals, blackmailing Red into following his orders and causing Maverick uprisings to draw in the Hunters' attention so that they could infiltrate the Crimson Palace. There, the Hunters confront Red, and upon being defeated he regrets being used by "The Professor" and sets part of the building to self-destruct, seemingly killing himself in the process.

Afterward, the Hunters confronted Sigma, and once defeated, a reborn Sigma punches Axl through a wall before vowing to X and Zero to again return in a new body.

Red, who had been defeated earlier and presumably killed, reappears, and Sigma attempts to possess him. Red is then revealed to be Axl taking on Red's form, who then proceeds to blast Sigma out of a window.

Unusually for most games in the X series, Sigma is not actually identified by name, even when he reveals himself.

Sigma's next plot was very complex, and it wasn't even him behind the entire scheme. It turned out that Axl was a prototype for a new generation of Reploids. These next-generation Reploids possessed advanced copy abilities, and Alia discovered that the copy chips bore copies of Sigma's program among other powerful Reploids. Sigma instigated a new Maverick revolt with these new Reploids as the humans were evacuating Earth in hopes of finding a new home on the Moon. However, the revolt was stopped, Sigma was completely devastated, and the real mastermind, Lumine, the manager of the Jakob Project, was revealed and beaten. Before his death, Lumine made a startling claim: according to Lumine, Sigma was destroyed for good and not returning.

It is believed that the reason Sigma would not regenerate within another body after his final defeat is that he was on the Moon, where due to the lack of available bodies to possess, the virus might have weakened in the vastness of space and got completely deleted. In addition, Sigma before dying for the final time asks in disbelief how X, Zero, and Axl could even beat him, before promptly saying "you couldn't...", implying alongside Lumine's prompt crushing of his remains head that Lumine may have weakened him somehow. There was also a lack of spare bodies, and his last body was hardly finished. However, his DNA is included in every copy chip of all the next generation Reploids so, technically, all New Generation Reploids are "infected" with the Sigma Virus, and possibly Lumine as well; meaning Sigma may return one day.

In the Legacy of Chris Thorndyke,

And he is voiced by David Kaye in the English dub and he is reprised by Mugihito in the Japanese dub.

THEMES

• Theme of Sigma (Marvel vs. Capcom Infinite) - The Commander Sigma
• Theme of Zero (Mega Man: Maverick Hunter X) - Sigma vs. Zero
• Catastrophe (Super Mario Galaxy) - Sigma turns... EVIL!
• Stage Select - Sigma (Mega Man X) - The Day of Sigma
• Encounter with Sigma (Mega Man: Maverick Hunter X)
• Sigma (Mega Man X) - Vs. Sigma - Phase 1 - MMX
• Sigma Transforms! (Mega Man: Maverick Hunter X) - Sigma transforms into Wolf Sigma
• Wolf Sigma (Mega Man X) - Vs. Sigma - Phase 2 - MMX
• Monkey by Showtaro Morikubo - The Resurrection of Sigma!
• Sigma (Mega Man X2) - Vs. Sigma - Phase 1 - MMX2
• Sigma Virus (Mega Man X2) - Vs. Sigma - Phase 2 - MMX2
• Sigma (Mega Man X3 - SNES) - Vs. Sigma - Phase 1 - MMX3
• Kaiser Sigma (Mega Man X3 - SNES) - Vs. Sigma - Phase 2 - MMX3
• Castle (Super Mario All Stars: Super Mario Bros.) - Dark Meeting with the General
• Remember Me?/Iron Gate (Sonic Adventure 2: Battle) - Double and Sigma
• Reaper Sigma (Mega Man X4) - Vs. Sigma - Phase 1 - MMX4
• Sigma - Phase 2 (Mega Man X4) - Vs. Sigma - Phase 2 - MMX4
• Castle of Koopa (Super Mario Bros. 3) - Sigma and a mysterious bounty hunter
• Sigma - Phase 1 (Mega Man X5) - Vs. Sigma Head/Sigma - Phase 1 - MMX5
• Gamma Sigma (Mega Man X5) - Vs. Sigma - Phase 2 - MMX5
• Death Ballad (Castlevania: Symphony of the Night) - "You have failed me, Gate!"
• Sigma - Phase 1 (Mega Man X6) - Vs. Reborn Sigma - Phase 1 - MMX6
• Sigma - Phase 2 (Mega Man X6) - Vs. Hell Sigma - Phase 2 - MMX6
• Sigma - Phase 1 (Mega Man X7) - Vs. The Professor/Sigma - Phase 1 - MMX7
• Sigma - Phase 2 (Mega Man X7) - Vs. Colossus Sigma - Phase 2 - MMX7
• Sigma - Phase 1 (Mega Man X8) - Vs. Sigma - Phase 1 - MMX8
• Sigma - Phase 2 (Mega Man X8) - Vs. Sigma - Phase 2 - MMX8
• ? - ?
• ? - ?
• Master of Puppets (Metallica) - The Nightmare of Sigma
• ? - ?
• Final Bowser Battle (Super Mario Galaxy) - The Final Battle! X vs. Sigma!