Sigma is a malevolent, sentient artificial intelligence who serves as the primary antagonist of the Mega Man X video game series. He was originally a Maverick Hunter and the most advanced Reploid ever developed, but became corrupted by a computer virus and turned Maverick. Since then, Sigma has schemed to conquer the world and destroy the human race, allowing Reploids to rule. Though he has been defeated in battle many times by Mega Man X, his digital consciousness has always managed to survive and download itself into a new body.
- 1 Personality
- 2 History
- 3 Appearance
- 4 Abilities
- 5 Weaknesses
- 6 Forms
- 6.1 Sigma (Original Body)
- 6.2 Wolf Sigma
- 6.3 Neo Sigma
- 6.4 Sigma Virus (X2)
- 6.5 Berserker Sigma
- 6.6 Kaiser Sigma
- 6.7 Sigma Virus (X3)
- 6.8 Reaper Sigma
- 6.9 Sigma Gunner
- 6.10 Earth Sigma
- 6.11 Sigma Head
- 6.12 Sigma Virus (X5)
- 6.13 Sigma "W"
- 6.14 Final Sigma "W"
- 6.15 Zombie Sigma
- 6.16 Hell Sigma
- 6.17 The Professor (Gunner Sigma)
- 6.18 Colossus Sigma
- 6.19 Copy Sigma
- 6.20 Belial Sigma
Sigma was calm and collected and an honourable leader until he turned Maverick. Since then, he has proven to be ruthless, power-hungry and manipulative. He is a Machiavellian schemer and a Darwinist, believing that humanity is weak and completely inferior to Reploids and as such should be destroyed so that the Reploid race will have the freedom it needs to evolve. While clearly insane, Sigma sincerely believes that his cause is righteous and is willing to use any means necessary to accomplish his goal of robot supremacy, even reducing the Earth to ashes if it means eliminating humanity. Time and again, he has manipulated the Maverick Hunters and their allies in order to further his goals and has almost destroyed the entire planet on more than one occasion. With each "death" he has suffered, he has become more and more obsessed with killing X and Zero.
As a Maverick Hunter
Sigma was among the first Reploids created by Dr. Timothy Cain, the scientist who had discovered X and built the Reploids based on his design. When the Maverick Hunters were established to surpress the increase in Reploid crimes, Sigma was appointed as commander of the organisation. He proved to be an excellent military leader and his combat skills were unmatched. Many of the other Hunters believed Sigma to be invincible, but they would be proven wrong in time.
One day, the Hunters encountered a red Maverick inside an abandoned factory. This Maverick turned out to be a vicious killing machine that managed to wipe out an entire Hunter unit. Refusing to let any more of his troops be sacrificed to this monstrous robot, Sigma entered the factory alone and fought against the Maverick. The red Reploid fought savagely and managed to cause heavy damage to Sigma, severing one of his arms and then proceeded to beat him to near-death. The Maverick almost tore off the commander's head, but suddenly became paralysed when a mysterious "W" symbol appeared on the energen crystal on his helmet. The Maverick clutched his head and cried out in pain, and Sigma used this moment to strike back, using his remaining arm to punch the crystal on the Maverick's head, shattering it and knocking out his opponent.
After the fight, Sigma and his men returned to Hunter Base with the inactive Maverick. Sigma was repaired and Dr. Cain studied the new Reploid, eventually reactivating it to find that the murderous, savage personality it had exhumed was gone. The Reploid identified itself as Zero and he was placed under Sigma's watch.
Unknown to Dr. Cain and the Maverick Hunters, Sigma had been infected by a virus during his first encounter with Zero, transmitted to his system when he smashed Zero's energen crystal. Sigma's programming was not only corrupted by the virus but seemed to merge with it, his consciousness becoming the "core" of the virus. His personality was twisted into a dark, malignant reflection of itself, lacking any compassion and convinced that the human race was holding Reploid-kind back, preventing them from reaching their full potential.
Sigma kept these thoughts a secret from Dr. Cain and continued to perform his duties as Hunter Commander, secretly plotting all the while on how to best bring about the fall of humanity. He managed to convince several of the Maverick Hunters to support him and also took a special interest in X, whom Dr. Cain had once stated possessed limitless potential. Eventually, the time came when Sigma initiated the first step of his revolution, sabotaging the Hunters from within and launching a missile strike upon Abel City, leading to a large number of human and Reploid deaths. X and Zero had attempted to stop him, but found themselves outmatched by Sigma's superior combat abilities. At one point, Sigma had grabbed Zero and X found himself hesitating to fire on Sigma for fear of harming Zero. Sigma questioned whether or not X truly held as much potential as Dr. Cain had claimed since X's compassion prevented him from stopping the missile launch.
Several weeks after the missile attack on Abel City, Sigma had built up an army and launched several attacks against the humans. The Maverick Hunters were mobilised, now led by Zero, who had entrusted X with making several precision strikes against Maverick-held locations. Zero himself would conduct an investigation to find Sigma's base of operations while X carried out the retirement of Sigma's lieutenants, all former Maverick Hunters that X had once worked alongside. As the battles went on, X grew in power as he discovered several items to enhance his systems, most notably the capsules that his creator Dr. Thomas Light had left behind.
When X and Zero found Sigma's base, they were confronted by his lieutenant Vile, who almost managed to kill X and would have done had Zero not sacrificed himself to save his friend. Following Zero's apparent death, X stood alone against Sigma's remaining forces and managed to obliterate anything that stood in his way. X eventually caught up to Sigma and the two fought, with X managing to destroy Sigma's body. However, Sigma's head remained active and fused to a new battle platform, which was immobile but still very powerful. X's new abilities that he had acquired saw him through the battle and Sigma was defeated, and with his destruction his fortress began to self-destruct. X narrowly escaped before the floating fortress sank beneath the ocean.
Although his physical form had been destroyed, Sigma's digital essence remained in cyberspace waiting to upload itself into a new body. Six months after the destruction of his fortress, Sigma was restored to the physical world by the X-Hunters: a trio of Mavericks who had supported his rebellion from the shadows and were now leading the remnants of his army. Sigma commanded the X-Hunters from behind the scenes as they salvaged the remains of Zero and challenged X to face them in order to regain Zero's parts.
X was able to retrieve Zero's parts and defeated each of the X-Hunters, provoking Sigma into revealing himself. Since he had been robbed of the chance to recruit Zero, Sigma settled for creating Dark Zero, a black-armoured mindless copy of the original. Before he could pit it against X, however, the rebuilt Zero appeared and destroyed the clone before it had the chance to act.
Sigma attempts to retreat, but X pursues him into the bowels of the Mother Computer complex while Zero goes to destroy the computer itself. X and Sigma battle and Sigma is destroyed once again, but before his program de-stabilises, Sigma expresses confusion as to why Zero did not join him, and goes on to state that "he is the last of the Doctor's creations". His program then de-stabilises as the Mother Computer is destroyed by Zero.
A year later, the Reploid scientist Dr. Doppler created a new vaccine to the Maverick virus which was hoped to prevent any further Maverick activity. Heralded as a hero, Doppler established his own utopian city known as Dopple Town. However, just weeks after Dopple Town's founding, a new wave of Maverick terrorism erupted and it was discovered that Dr. Doppler's vaccine was merely a placebo. With an army of Maverick Reploids under his command, the doctor attempted to finish what Sigma had begun and conquer the world.
X and Zero led the Maverick Hunters against Doppler's forces and would eventually confront the doctor in his underground lab. X battled against Doppler personally and defeated him, though he did not kill him. The wounded Doppler appeared to come to his senses, revealing that Sigma had corrupted him and manipulated him into building a powerful new battle body. The doctor told X that the body was stored in a hangar below the main lab and so X hurried to find the body and destroy it before Sigma occupied it.
X was too little too late and Sigma was revealed to be alive and well, sporting a new body equipped with a boomerang shield. X was able to destroy this body, but Sigma's consciousness then occupied the new "Kaiser" battle body that Doppler had built. While Sigma's "Kaiser" form was indeed very strong, it was not indestructible and X just managed to destroy it. The explosion of Sigma's body caused heavy damage to the lab complex, causing molten lava to pour inside. As X tried to escape the rising lava, Sigma's viral form appeared and attempted to possess him. X was weakened and cornered and his weapons could not affect Sigma's non-corporeal virus state. However, X was saved at the last minute by Zero, who had a Sigma anti-virus installed into his Z-Saber by Dr. Doppler and was able to strike Sigma with it. Sigma then disappeared, apparently destroyed by the anti-virus, and X and Zero escaped Doppler's lab before it was completely destroyed.
The Repliforce Coup
In Mega Man X 4, Sigma had returned again, though it is unknown who had built his new body. With the new Repliforce army aiding the Maverick Hunters in surpressing Maverick activity, Sigma attempted to pit the two parties against each other. He contacted the General of the Repliforce and warned him that the Hunters were a potential threat that needed to be destroyed. The General dismissed Sigma, refusing to betray the humans he was sworn to protect.
Sigma planted his own agents within both Repliforce and the Maverick Hunters, who each worked toward building tensions between the two parties. One of the Mavericks sabotaged the airborne city of Sky Lagoon, causing it to fall upon the city below and destroying them both, wiping out both populations. Since Repliforce units were present in Sky Lagoon at the time of its descent, the Maverick Hunters demanded that Repliforce disarm and submit themselves to questioning. When they refused, the entire Repliforce were all labelled as Mavericks.
In response to the humans and Hunters' incorrect judgment, the General made an announcement to his troops that Repliforce was to establish its own independent nation, thereby rebelling against humans in the name of Reploid rights. Unfortunately, by instigating a coup, Repliforce were playing right into Sigma's hands, who continued to monitor the conflict between Repliforce and the Maverick Hunters through the spies he had planted in both groups.
Sigma only revealed his part in the conflict when X and Zero had boarded the Final Weapon, an orbiting space station that was to serve as Repliforce's utopian nation. Sigma had taken control of the Final Weapon and had aimed it at Earth, but he was confronted by his old foes once again. Sigma was defeated, but the Final Weapon was ready to fire, and only the sacrifice of the General could stop it. Earth survived, but Repliforce was left in shambles.
The Earth Crisis
Some time after the fall of Repliforce, humanity began the development of orbital habitats, leading to the construction of the space colony Eurasia. Sigma, who had again been revived by an unknown party, hired the Reploid mercenary Dynamo to sabotage the colony with a virus that would disrupt the colony's orbit, causing it to collide with Earth and completely destroy the entire planet. At the same time, Sigma had been building up enough power to spread the Sigma Virus all over the globe, infecting countless Reploids at once. This plot would allow Sigma to not only destroy humanity but also awaken Zero's "true self", by exposing him to high levels of the virus.
Sigma enacted his plan by triggering a Maverick outbreak in order to attract the Maverick Hunters' attention, and surely enough, X and Zero arrived on the scene. Sigma attacked the two Hunters and they defeated him, but he had lost to them on purpose. As Sigma's physical form exploded, his viral essence suddenly swept over the Earth, causing countless Reploids to go Maverick. His core consciousness would re-coalesce in a new body and he would watch from the shadows as the Maverick Hunters tried desperately to find the resources they would need to stop the Eurasia Colony from destroying the planet.
The Hunters were only partially successful, however. The colony was destroyed, but debris from its explosion rained down over much of the planet, devastating the environment and forcing the human race underground while Reploids remained on the surface to repair the damage. The largest portion of Eurasia debris was giving off unusual energy readings which the Hunters verified as the formation of a new virus, created by the fusion of the Sigma Virus and the virus that Dynamo had used to sabotage the colony. When X and Zero investigated the crash site, Zero began to exhibit a significant increase in power as the virus - which had been dubbed as the "Zero Virus" - infected him. Concerned for his friend's well-being, X urged Zero to return to base, but Zero was adamant about continuing the investigation as he began to see strange images concerning his forgotten past. Fearing that Zero's exposure to the virus might compromise the mission, X tried to force Zero to return to Hunter Base. The two friends fought each other and Sigma looked on from the shadows, intent on destroying whoever was left standing himself.
X and Zero exhausted themselves fighting each other and Sigma tried to take advantage of the moment by attacking X. Zero, however, protected X from Sigma's attack, prompting the Maverick into withdrawing. The two Hunters took a moment to recuperate before pursuing Sigma and caught up to him in the deepest area beneath the Eurasia ruins. Sigma revealed his plan to try and awaken Zero's original persona by scattering the Sigma Virus and threatening the Earth with the colony and he also made mention of an unidentified partner who had assisted him: an old man who knew all about Zero and claimed to be his "father".
X and Zero battled Sigma once more and appeared to have destroyed him, with Zero being critically damaged during the fight. Sigma's remains were still active, however, and fired an energy beam at X and Zero when they had dropped their guard. Both Reploids were nearly killed in the blast, but Zero used what little energy he had left to fire off a buster shot at Sigma, finishing him.
Three short weeks after the fall of Eurasia, the Reploid scientist Gate was studying the crash site when he discovered a piece of debris that carried traces of the Zero Virus. While studying the fragment, Gate is infected by the virus and goes Maverick, deciding that he will create a new breed of Reploids that will dominate the world. He later returns to the Eurasia site for additional materials and finds Sigma's remains amidst the rubble, taking them back to his laboratory for reconstruction.
When X and Zero later confront Gate in his lab, Gate plays his trump card and reactivates Sigma. Sigma's body is still incomplete, however, and his mental faculties are severely impaired from when he stretched his viral program so thin during the Eurasia incident, and so he cannot speak, or even think, coherently. Sigma does not acknowledge Gate's part in restoring him and simply kills him before moving on to attack X and Zero. While still battle-capable, Sigma does not stand much of a chance against the Hunters in his incomplete state and is easily defeated.
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 infiltate 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.
Afterwards, 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.
The Jakob Project
Sigma would return in Mega Man X 8, this time instigating a new Maverick rebellion utilising the New Generation Reploids born of the Jakob Project. The director of Jakob, Lumine, had replicated the Copy Chip that Axl possessed and had imprinted Sigma's DNA onto the chips, allowing his legion of Guardroids to assume Sigma's form.
With a new army of advanced Reploids that he regarded as his "children" (since they carried a portion of his programming), Sigma attempted to sabotage humanity's efforts to colonise the Moon. He established his own base there, intending to relocate all of Reploid-kind and then destroy Earth and its human population. X, Zero and Axl pursued him to the Moon and fought against him one last time, apparently destroying him for good. It was then revealed that Sigma hadn't been acting alone and that Lumine - formerly believed to have been kidnapped by Sigma - had actually been working with him willingly. The Maverick Hunters were also successful in defeating Lumine and revealed his Maverick status to the public. The Jakob Project was then scrapped and all next-gen Reploids baring the Copy Chip were dismantled.
Post X era
Sigma never returned following his last encounter with X on the Moon. Since there was a lack of suitable bodies to inhabit upon his destruction, it is possible that Sigma's core essence degraded. However, since all of the Next Generation Reploids carried Sigma's DNA, it is also feasible that Sigma could've been restored via one (or all) of them.
Even though Sigma's "soul" was finally destroyed following Mega Man X8, the Sigma Virus remained on Earth and continued to cause Reploids to go Maverick. Luckily, scientists were able to eventually develop a "Sigma Antibody Program" thanks to extensive research on Zero, who still carried the virus. With a cure discovered for the virus, Maverick Reploids were all treated with it, thereby finally erasing every last trace of Sigma forever and bringing an end to the Maverick Wars.
While Sigma has utilised various different bodies over the years, his primary bodies have all been humanoid. All of his bodies, primary and secondary, have maintained the appearance of his first body's head: bald, without a helmet or other headpiece, deep blue eyes with scar-like marks running over them, and a red jewel attached to his forehead.
Sigma's different bodies have all possessed their own set of powers. Common abilities that Sigma has wielded in any form are his tactical knowledge and expertise, and most notably his ability to spread the Sigma Virus and corrupt other robots. Depending on Sigma's whim, Reploids he has infected can go completely berserk and attack anything and anyone indiscriminately, can become loyal to him and agree with his way of thinking, or Sigma can control his infected victims like mindless puppets.
As far as physical weaknesses go, each of Sigma's bodies can be strongly affected by certain weapons and attacks. But Sigma's greatest weakness, however, is is over-confidence. Every time he has battled X, Zero and Axl, he has always expressed an assuredness of his victory, certain that despite the powers each has attained, he is still the stronger and more capable fighter. He has always been proven wrong in this regard and each defeat has only served to fuel his insane obsession with destroying X and Zero.
Sigma has used a multitude of different bodies in his battles against the Maverick Hunters, each possessing their own abilities, strengths and weaknesses. Each of these bodies has been detailed below.
Sigma (Original Body)
Sigma's first body, created by Dr. Cain. It does not possess as many weapons as some of his later forms, but it is among his sturdiest bodies, capable of high endurance and mobility. His primary weapon in this form is his beam saber, which he uses to make precision attacks against his foes' weak spots.
- Beam Saber - Sigma tends to dash and leap about while wielding this weapon. He can inflict heavy damage and also deflect attacks with the energy blade.
- Overload Laser - Sigma can fire rapid laser pulses from the crystal on his forehead.
- Electric Spark - A powerful electrical surge can disrupt Sigma's circuitry.
When Sigma's original body was destroyed by X, his head survived intact and connected itself to this large immobile platform installed within his fortress's command chamber. This form bears a resemblance to Sigma's pet wolf Mechaniloid Velguarder and is equipped with larger, more powerful versions of Velguarder's own weapons. Two hovering clawed hands would attempt to crush X beneath them, but X was able to use them as platforms to attack Sigma's head, his only weak spot.
- Fire Breath - A stream of flame is fired from the wolf's mouth that sweeps across the floor, toasting anything caught in its path.
- Electric Orb - Multiple blasts of electricity are rapidly fired from the wolf's mouth in the same sweeping pattern as Fire Breath.
- Claw Thunder - Wolf Sigma's clawed hands can fire narrow electrical blasts from both the top and bottom of the hand, so X is in danger even when standing on top of one of them.
- Rolling Shield - Armoured Armadillo's weapon is the only thing besides the X-Buster that can damage Wolf Sigma.
- X-Buster - X's buster can damage Sigma's head, but the damage is minimal and only works when fired at maximum charge (either with the X1 Armour or with Zero's buster).
Sigma's new body in Mega Man X 2 was created by the X-Hunter Serges. This body surpasses the original in speed and dexterity. It is equipped with three long metal claws on both forearms which can rend through opponents with ease and are also useful for blocking attacks.
- Slash Smash - When Sigma strikes X with his claws, he sends X hurtling into a wall for greater damage.
- Plunging Claw - Sigma teleports and reappears above X's head, dropping down to strike him with his claws.
- Electric Spark - This attack is similar to the Electric Spark used by X when he copied Spark Mandrill's power in X1. Sigma surrounds himself in five electrical orbs and launches them in quick succession towards his opponent. He can even fire a more powerful version called the Electric Wall, a wall of electricity that completely fries any robots caught in its path.
- Sonic Slicer - Sigma's lighter framework makes him susceptible to Overdrive Ostrich's weapon.
Sigma Virus (X2)
When his Neo form is defeated, Sigma counter-attacks X as a large wire-frame hologram of his own head. The hologram is solid and is generated by the Mother Computer. While X appeared capable of attacking this hologram, it's possible that Sigma was only defeated when Zero destroyed the computer.
- Laser Breath - Sigma's mouth opens to rain down a destructive laser beam and sweeps the boss-room floor with it.
- RepliSphere - The Sigma Virus generates holographic spheres that can damage X. These spheres can change into small Mechaniloid enemies: Fishern, Tiranos and Tubamail-S.
- Viral Wrap - When its health is low, the Sigma Virus will change its attack pattern and start teleporting around the boss-room attempting to envelop X. If he manages this, Sigma can slowly drain away X's health.
- Strike Chain - Aside from the X-Buster, only Wire Sponge's weapon can damage Sigma's viral form.
- X-Buster - The X-Buster can damage the Sigma Virus, but only charged shots will have any effect.
Sigma's primary body in Mega Man X3. This form was created by Dr. Doppler and came equipped with a circular shield that could be thrown like a boomerang. Like his first body, this form could leap around a lot and rain down fire upon enemies.
- Fireball - Sigma can constantly launch fireballs from his arm in this form.
- Boomerang Shield - This energised shield could not only deflect incoming weapons but could be thrown like a boomerang and slice through opponents. It initially circles around the room once when thrown by Sigma, but when his health is low enough it will circle around twice.
- Frost Shield - Berserker Sigma is vulnerable to this weapon as his body has an affinity for fire.
- Spinning Blade - While Sigma's shield is extremely durable, his actual body is not as tough and can easily be torn apart by the Spinning Blade.
The ultimate battle body created by Dr. Doppler. This huge humanoid form was heavily armoured and sported a wide array of weapons. As powerful as Sigma had boasted, his Kaiser body was not invincible and could be damaged by attacking the head.
- Hovering - Hover-jets were built into the boots. Due to the sheer size and weight of the body, it could not achieve full-on flight.
- Homing Bomb - Small, spherical bombs that would seek out targets.
- Missiles - Sigma could fire a spread of missiles from his shoulders.
- Wide Beam - Two beam cannons hanging from Sigma's shoulders that fired expansive energy rays that could make short work of even the toughest Reploids.
- X-Buster - As is typical for Sigma's final forms, Kaiser Sigma's only weak point is his exposed head. Kaiser Sigma is so heavily armored that only the X-Buster can damage him.
Sigma Virus (X3)
When his Kaiser body is destroyed, Sigma re-appears in his viral form, which once again appears as a holographic wire-frame of his head. As lava floods Dr. Doppler's lab, X must wall-climb up a long shaft to escape. The Sigma Virus hovers up with him and attempts to possess him. X was unable to affect the Sigma Virus with any of his weapons and could only try to avoid it.
After escaping the rising lava, X finds himself cornered in a dead-end corridor. Before Sigma can possess X's body, Zero appears behind him and strikes the Sigma Virus with his Z-Saber, which Dr. Doppler had modified with an anti-virus patch. Sigma appears to de-stabilise and is believed to be erased, but he inevitably returns again in Mega Man X4.
Sigma's primary body in Mega Man X4. It is unknown who created this body, but it possesses more weapons than is typical of a primary Sigma body. It has high defense and even the cloak Sigma wears in this form, while appearing to be made of simple cloth, actually provides additional protection. This body has been unofficially dubbed "Reaper Sigma" due to its dark cloak and the energy scythe it carries, giving Sigma the appearance of the Grim Reaper.
- Scythe Dash (Phase 1) - Sigma dashes through the air, wielding his scythe to slice through his opponent.
- Death's Shadow (Phase 1) - Sigma hovers above his foe and casts a shower of energy spheres down upon them.
- Boomerang Scythe (Phase 2) - Sigma leaps into the air and throws his scythe, which spins and flies in a circular pattern, coming back to him.
- Death Shock (Phase 2) - Sigma throws his scythe at his opponent and it will embed itself in either the wall or the floor, sending electrical surges through the surface. Depending on whether the wall or floor was electrified, Sigma will follow up with one of the two following attacks.
- Eye Laser - If Sigma's Death Shock hits the wall, he will then fire lasers from his eyes, standing by the opposing wall as he does so that the beams stretch from one end of the boss-room to the other.
- Flying Sickle - If the Death Shock electrifies the floor, Sigma will leap into the air and hover there, launching small boomerang-shaped projectiles. These projectiles home in on wherever the enemy is located.
- Rising Fire - When Sigma is wrapped in his death cloak, only fire-based weaponry will harm him. Absolutely nothing else will work.
- Lightning Web - Web Spider's weapon will paralyse Sigma's circuitry momentarily.
This is one of two secondary forms Sigma takes in Mega Man X4. This body is fused into the architecture of the Final Weapon and appears to be some kind of heavy guard robot with Sigma's face fused to its helmet. It carries a large laser rifle that fires wide beams and will occasionally sweep the entire deck with a more focused beam. Sigma's face is the only part of it that can be damaged and it takes greater damage from the Soul Body or Zero's Ryuenjin attack.
Sigma's other secondary form in MMX4. It appears to be a giant disfigured head that has been fused to the Final Weapon via multiple conduits and cables. It does not move but attacks by attempting to inhale X or Zero and basically eat them. Its other method of attack is to exhale, blowing X and Zero away into spiked walls and also by spitting out chunks of shrapnel. It is vulnerable to the Ground Hunter drones and Zero's Shippuuga technique.
This is Sigma's first form in Mega Man X5 and serves as the boss of the intro stage. It is a large robotic head that flies using engines on the back of it. It attacks using various energy projectiles: a large sphere fired from its eye, a spread of small projectiles from its mouth and also a large laser blast. As the intro boss for MMX5, X and Zero have no special weapons when they encounter the Sigma Head. Its weak point is its mouth cannon.
Sigma Virus (X5)
After his Head form is destroyed, Sigma scatters the virus all across the world. X and Zero encounter numerous Sigma viral entities across different areas which all appear as small Sigma Heads made of a sickly purple vapour. The virals move slowly but are unhindered by attacks, obstacles or terrain and will relentlessly follow X and Zero. X will recieve damage if infected too many times, but oddly enough Zero's power increases when he is infected. This was all a part of Sigma's scheme to awaken Zero's true persona by using the virus to "purify" him.
Sigma's primary body in MMX5 was created by his unseen, unnamed benefactor (speculated to be Dr. Wily). It appears to be sleeker and lighter than his other bodies and has no carried weapons like a sword or scythe, but it is capable of various energy attacks. When he first appears to confront X and Zero, Sigma is wearing purple body armour with a flowing cape of violet light. It is unknown how much extra protection it grants since Sigma takes it off and discards it before the battle begins.
- Energy Ball - Sigma fires multiple energy balls in a wave pattern, shifting up and down as they go.
- Energy Wave - A huge air-splitting wave that takes up most of the height of the boss room, making it difficult to avoid.
- Virus Shield - Sigma generates a barrier around himself to block incoming attacks. The barrier resembles his head.
Sigma "W" is poorly insulated against electrical attacks and so takes greater damage from the Tri-Thunder and E-Blade weapons.
Final Sigma "W"
Sigma's secondary body was also built by his anonymous partner, though this body had yet to be completed by the time X and Zero arrived to confront him. Nevertheless, it proved to be quite capable. It would materialise in the background to attack and would briefly de-materialise at times. It used various energy attacks as well as two large modular fists to crush X and Zero. Its weak spot was the gem on its forehead.
- Sigma Knuckles - The two disembodied hands would fly in and attempt to crush X and Zero beneath or between them. They could also fire dark energy blasts from their palms. The hands could be destroyed but would be replaced after a short while.
- Homing Plasma - Sigma's eyes fired balls of plasma that would shift position depending on X's location.
- Sigma Cube - Sigma could generate cubes of energy that would spontaneously appear in the boss-room wherever X or Zero was positioned.
- Due to the incomplete nature of this body, Gamma Sigma is particularly weak to Axle the Red's weapons; the Spike Ball can penetrate his unfinished chassis and the Twin Dream makes it easier to break through Sigma's defenses.
Sigma's primary body in Mega Man X6. It was created by Gate but had yet to be completed before X and Zero raided Gate's laboratory. Most of the body cannot be seen as it is always covered by long, tattered robes. Even Sigma's consciousness is only half-formed, having not yet fully coalesced after spreading the Sigma Virus across the planet in MMX5. His mind may be fragmented, but he still remembers his rage towards X. This incomplete body possesses many energy attacks, but its movements are painstakingly slow. Amongst all of Sigma's bodies, this one is probably the least threatening.
- Spark Shot - Sigma spits an electrical blast from his mouth.
- Plasma Barrier - Sigma throws up a wall of plasma that pushes toward the enemy. The barrier can be pushed back by buster fire.
- Energy Shrapnel - After being hit by a strong-enough blast, Sigma will topple over and scatter several energy projectiles as he falls.
- Dark Wave - Sigma throws waves of dark energy towards his opponent.
This form of Sigma is already rather weak, but takes greater damage from heavy-impact weapons like the Metal Anchor weapon and Zero's Rakukojin technique.
Hell Sigma is a giant humanoid form constructed by Gate. Like the previous form, this body is incomplete but still possesses a wide range of attacks. It can also summon small, slimy drones for assistance.
- Vertical Laser - A pillar of laser fire appears when Sigma opens his mouth. A targetting reticule appears on the floor where the pillar will appear.
- Plasma Laser - Sigma fires a large horizontal plasma beam from his mouth cannon.
- Skull Drones - Sigma fires a number of energy orbs from the gem on his forehead. These orbs then form into skulls and can move either byt slowly oozing across the floor and ceiling. They attack by firing energy shots from their mouthes.
- Dark Spark - Sigma fires a small electric orb from his mouth cannon in a downward diagonal pattern. When the orb touches the floor, it instantly expands to a giant crackling sphere that rapidly shoots along the floor. It is very difficult to dodge.
Hell Sigma's weak spot is the cannon in his mouth. It is most vulnerable to the Magma Blade and Zero's Ensuizan technique.
The Professor (Gunner Sigma)
Sigma went by the alias of "The Professor" during Mega Man X7, so the name could also apply to his primary body in that game. Unofficially, he has also been referred to as "Gunner Sigma" due to the long twin-barreled rifle he carries. His rifle can actually split into two separate weapons, giving him a broader attack range.
- Hovering - Sigma hovers in the background when performing his secondary attack pattern.
- Teleport - Sigma can teleport to different sides of the boss-room or into the background.
- Bound Shot - When Sigma's guns are joined together, they fire small energy shells that can bounce off surfaces.
- Rapid Fire - For his secondary attack, Sigma teleports into the background and splits his rifle in two. Wielding two guns, he fires a rapid spread of energy bullets at his foes.
- Laser Cannon - Sigma wields a large cannon that fires a devastating laser blast.
Gunner Sigma's heavy weaponry severely reduces his agility, leaving him vulnerable to high-speed attacks like the abilities that X, Zero and Axl obtain from Wind Crowrang.
Sigma's secondary form in MMX7. This body is a gigantic humanoid form and bigger than any of Sigma's previous bodies.
- Plasma Bomb - Sigma fires several large balls of plasma from his hands and up into the air. The projectiles will then fall down upon the platforms closest to the enemy.
- Belt Laser - Sigma fires a laser beam from the energen sphere on his waist.
- Fireball - Sigma shoots fireballs from his mouth directly at the opponent. Zero is capable of using his Z-Saber to reflect the fireballs back at Sigma to damage him.
- Colossal Punch - Sigma flies towards the enemy to deliver a powerful punch with his huge fist.
Colossus Sigma is vulnerable to the abilities learned from Splash Warfly, Soldier Stonekong, and Vanishing Gungaroo, all of which have the capacity to break through Colossus Sigma's many layers of armor.
This is Sigma's first form in Mega Man X8, however he does not fight the Maverick Hunters himself in this form. What X, Zero and Axl battle against may look like Sigma, but in fact they fight a New Generation Reploid that has assumed Sigma's form. Sigma did inhabit a body like this but transferred his consciousness to a new body prior to his final battle with the Hunters.
This body appears to be an updated version of Sigma's very first body, both in appearance and ability.
- Saber Dash - Dashes forward and slashes with his beam saber.
- Scorch Laser - Fires a focused laser beam from his forehead gem and scorches the entire floor.
- Doom Buster - Charges up a massive energy blast that is fired from his hand.
- Reflect Magnum - Fires multiple small projectiles that bounce off of surfaces.
Copy Sigma is vulnerable to all abilities obtained from Dark Mantis.
Sigma's final body, dubbed as "Belial Sigma" due to its demonic appearance. This body was built by Lumine but had yet to be completed before Sigma occupied it. Still, it possessed combat ability equivalent to Sigma's first body with the addition of some new skills.
After this final body was destroyed, Sigma's core program died with it, meaning that he could not return again.
- Sigma Blade - A large great sword that serves as Sigma's main weapon in this form. He performs dash attacks and can also surprise his foes by teleporting and reappearing above them, bringing the blade down upon their heads.
- Laser Ring - Sigma fires rings of energy towards his opponents. It is possible to dash through the rings to avoid damage.
- Scorch Laser - A focused laser beam that Sigma uses to set the walls on fire.
Belial Sigma is vulnerable to all abilities obtained from Optic Sunflower.