||This article describes a work or element of fiction in a primarily in-universe style. (October 2009)|
The Legacy Virus storyline ran through various Marvel comics titles from 1993 to 2001.
The Legacy Virus was actually a viroid and was released by Stryfe, a terrorist (and clone of Cable raised by Apocalypse) from approximately 2,000 years in the future. It originally existed in two forms, Legacy-1 and Legacy-2, but later mutated into a third form, Legacy-3; all were airborne agents.
Legacy-1 and Legacy-2 searched for a target organism's "X-factor," the sequence of mutant genes that gave a mutant his/her superpowers. If it did not find an activated X-factor in the target, the viroid would die off, leaving the person completely unaffected. If, however, it did detect the X-factor, it would begin inserting introns (junk DNA sequences) into the transcription codings of the victim's mutant RNA, the process commonly being triggered after the patient used their powers for the first time after contracting the disease. The result was a major compromise of the replication and transcription process so disruptive as to eventually render the body incapable of creating healthy cells, ultimately resulting in the death of the victim. Prior to death, the viroid causes its host's powers to flare out of control.
Legacy-1 attacked general transcription and replication of all cells, a messy and non-selective process that resulted in a condition akin to a fast-replicating cancer. This is the version that infected Illyana "Magik" Rasputin, sister of Piotr "Colossus" Rasputin.
Legacy-2 was much closer to Stryfe's original template and more in tune to his desire to stir a species war between humans and mutants. Its attacks were selective, working only on the X-factor genes. The net result was that a victim would eventually lose control of his superhuman powers. In addition to developing at a far slower rate than Legacy-1, victims of Legacy-2 developed skin lesions, fever, cough and overall weakness (symptoms displayed by the telepathic X-Man Revanche). The slow nature of Legacy-2 is why St. John "Pyro" Allerdyce survived for years following his initial infection.
Legacy-3 was a complete fluke, accidentally created in the body of the mutant woman known as Infectia. Her powers allowed her to scan and visualize the genetic structure of a living being and then alter it according to her own whims; she was essentially a walking genetics laboratory. Infectia had herself been infected with the Legacy Virus, which her own powers tried to stave off. In doing so, they caused a replication error in the Legacy-2 viroid that was killing her. The viroid's conditioning to infect only if the X-gene was found in the host was stripped. When Henry "Beast" McCoy opened Infectia's containment chamber in an act of compassion to allow her one final look at the night sky, he inadvertently released this new "free agent" strain[volume & issue needed]. Legacy-3 was capable of infecting any living being that fit within the parameters of its general original template; that is, hominids only, not canines, felines, etc. Moira MacTaggert, long-time ally of the mutant X-Men and one of Earth's top geneticists, seemed to have been the first non-mutant human to be infected with Legacy-3.
Mystique had also created (or commissioned the creation of) a strain of the Legacy viroid that only attacked non-mutant humans, leaving mutants completely untouched.
The Legacy Virus was based on a virus created by Apocalypse in the distant future, which was intended to kill the remaining non-mutants. At the time that this alternate version of Apocalypse was killed, the virus had not been perfected, and much like Legacy-3, it targeted all humans indiscriminately. As a result, this virus was never deployed, until Stryfe acquired it and altered it for his own purposes.
During the X-Cutioner's Song crossover, the villain Stryfe gave Mister Sinister a canister that he claimed contained 2,000 years worth of genetic material from the Summers bloodline. When Gordon Lefferts, a scientist working for Sinister, opened the canister after Stryfe was apparently killed by Cable, they found nothing inside. Far worse than that, the canister actually contained a plague, Stryfe's "legacy" to the world.
The virus raged on for some time in the mutant population, until Mystique, in an effort to make the world safe for mutants, modified the virus to affect only humans[volume & issue needed]. When Moira found out about this strain of the virus, she finally grasped what the key to the cure was. Unfortunately, she was mortally wounded by Mystique during the Brotherhood of Mutants' attack on Muir Island and did not live to complete the cure. Professor X did manage to telepathically retrieve the critical information before Moira died.
With this information, Beast was able to synthesize the cure a few weeks later, though one that had a price; the virus had first been released by the death of the first victim, and the release of the cure would have the same effect. Colossus, who did not want any more people to suffer his sister's fate, snuck into McCoy's lab and injected the cure into himself and activated his mutant powers, transforming his body into organic steel. This "supercharged" the Legacy cure, simultaneously killing him and stopping the spread of the Legacy virus, instanteously curing even those dying of the virus at that moment (Although it was later revealed Colossus had been resurrected by alien technology and was being used as a test subject for an experimental formula that would reverse mutations before he was rescued by the X-Men).
Unfortunately, this rapid cure had unforeseen geopolitical effects. Thousands of Legacy-infected mutants had been quarantined on the island nation of Genosha, which was controlled by Magneto at the time. The instant cure gave Magneto a vast army overnight and allowed him to begin carrying out his plans for world conquest in the Eve of Destruction crossover.
In X-Factor vol. 3 #10, it was revealed that Singularity Investigations was creating a virus designed to kill mutants. While Jamie Madrox referred to this as the Legacy Virus, it is unclear whether Singularity is actually recreating Stryfe's virus, creating what is to later actually be Stryfe's virus, or merely engineering a new one with a similar purpose.
In X-Force #7, The Vanisher is seen to be in possession of a mutated strain of the Legacy Virus. It was later destroyed by Elixir in X-Force #10.
During the Skrull Invasion of Earth, Beast discovers that the Legacy Virus can infect Skrulls as well. Beast ponders whether to use it against the invading aliens. Cyclops decides to use it to get the Skrulls to surrender.
The Legacy Virus has returned once more as it turned out there were other samples that fell into the hands of Bastion. Samples have been injected into Beautiful Dreamer and Fever Pitch by the Leper Queen in order to cause their powers to go berserk and kill themselves and thousands of humans during an anti-mutant rally held by the Friends of Humanity. It was later revealed that Hellion and Surge were also injected with the Legacy Virus.[volume & issue needed]
Infection list 
Listed below in alphabetical order are the Mutants (with their powers) infected by the Legacy Virus:
|Character||First Appearance of Infection||Notes|
|Absalom||X-Force (vol. 1) #37 (August 1994)||Virtual immortality, ability to extend razor-sharp spines from his body. Killed by Selene in X-Force (vol. 1) #54 before the Legacy Virus could claim him.|
|Abyss||Cable (vol. 2) #40 (February 1997)||Malleable body houses a dimensional vortex. Was saved from death when Colossus sacrificed himself to release the cure.|
|Aminedi||X-Men Annual Vol. 2 #2||Air Particle Transformation. Dies from the Legacy Virus.|
|Avalanche||Powerful vibration generation. Survived the Legacy Virus.|
|Bolt||X-Men Unlimited (vol. 1) #8 (September 1995)||Bio-Electric generation/manipulation. Survived the Legacy Virus.|
|Burke||X-Force (vol. 1) #34 (August 1994)||Killed by the Virus.|
|Feral||X-Force (vol. 1) #37 (August 1994)||Feline appearance. Survived the Legacy Virus.|
|Infectia||X-Men (vol. 2) #27 (December 1993)||Mutagenic touch. Killed by the Legacy Virus in X-Men (vol. 2) #27 (December 1993).|
|Gordon Lefferts||X-Men (vol. 2) #23 (December 1993)||Telekinesis and Telepathy. Revealed to have been the first victim killed by the Legacy Virus in X-Men (vol. 2) #27 (December 1993)|
|MacTaggert, Moira||Excalibur (vol. 1) #80 (August 1994)||Publicly designated as the first human to contract the Legacy Virus in X-Men Prime. Killed by Mystique before the Legacy Virus could claim her.|
|Madrox, Jamie||Duplicate infected in X-Factor (vol. 1) #91 (June 1993).||Duplicate died from Virus in X-Factor (vol. 1) #100 (March 1994).|
|Magik (Illyana Rasputin)||Magic user, chrono-variant teleportation. Killed by the Legacy Virus in Uncanny X-Men #303 (August 1993). Later revived.|
|Mastermind||Illusionist. Killed by the Virus in Uncanny X-Men Annual #17.|
|Maverick||Healing factor put Virus into remission.|
|Mister Sinister||Immortal. May have been infected. Though if so, his own healing factor must have greatly slowed its progression, nevertheless saved when Colossus sacrificed himself to release the cure.|
|Mutate #24601||Only Genoshan Mutate "named"; many others infected and presumed killed.|
|Nicodemus||X-Force (vol. 1) #20 (March 1993)||Undefined fire-based abilities. Revealed to have been killed by the Virus in the same issue.|
|Pyro||X-Men Annual (vol. 2) #2.||Psionic manipulation (but not generation) of fire. Killed by the Virus in Cable (vol. 2) #87 (Jan 2001) after saving Senator Robert Kelly from an assassination attempt.|
|Psynapse||Was "killed" by teammates for being infected and causing him to be "unfit". Revealed to have tricked his teammates and saved from death when Colossus sacrificed himself to release the cure.|
|Revanche||X-Men Annual (vol. 2) #2.||Telepathy, psionic blade generation. Mercy-killed by Matsu'o before she succumbed to the Virus in X-Men #31 (April 1994).|
|Numerous X-Skrulls||Secret Invasion: X-Men #4||Powers based on the X-Men.|
|Beautiful Dreamer||Behind the scenes prior to X-Force (vol. 3) #12.||Injected with the Legacy Virus by the Leper Queen to be used as a biological weapon, killing thousands of humans and herself.|
|Fever Pitch||X-Force (vol. 3) #12.||Similar fate to Beautiful Dreamer, perishing along with hundreds of other humans in a wave of fire.|
|Hellion||X-Force (vol. 3) #13.||Captured by the Leper Queen and injected with the Legacy Virus to be used as a biological weapon. Healed from the Legacy Virus by Elixir.|
|Surge||X-Force (vol.3) #13.||Similar fate to Hellion. She was healed from the Legacy Virus by Elixir.|
Other versions 
Ultimate Marvel 
Created by Nick Fury, Beast is held by S.H.I.E.L.D. to try to find a cure for it. But there are no recorded infections, yet. Bishop explains the Virus is another attempt by Fury to replicate the Super Soldier experiment that created Captain America, with a vital ingredient being Beast's blood by Admiral William Stryker. For all intents and purposes, the formula does turn normal humans into super-strong beings, but if it comes into contact with mutants, it kills them. So Fury held Beast so he could find a cure, as Fury refuses to bring the project to his superiors without clearing the infection detail up.
In other media 
- In X-Men, a variation of the Legacy Virus was used in a brief storyline where it was the creation of Apocalypse, who had created the virus with the aid of Graydon Creed and the Friends of Humanity, infecting innocent people and claiming that mutants were the ones who had caused the plague. In an attempt to stop the plague, Bishop came back from the future to destroy Apocalypse's work before the virus could move on to mutants, but as a result vital antibodies that would allow the mutant race to survive future plagues were never created. Traveling back from even further in the future, Cable was able to come up with a compromise that allowed both Bishop's and his own missions to succeed; although the plague never made the jump to mutants on a large-scale basis, Cable nevertheless ensured that Wolverine would be infected, thus creating the necessary antibodies while not killing any mutants thanks to Wolverine's healing factor.
Video games 
- In X-Men 2: Game Master's Legacy, the game's plot centers around the X-Men and the Legacy Virus.
- In the video game Marvel: Ultimate Alliance, a side mission includes saving a S.H.I.E.L.D. Omega Base Computer (which contains research data on the Legacy Virus) from being destroyed by 3 out of 5 Super Soldiers. This is one of many side-missions that do not appear in any menus or maps. The computer is located in a room that is on the path from the elevator leading to the elevator that heads to the top of the S.H.I.E.L.D. Omega Base. If it is saved from being destroyed, its information will be used to make a cure several years later that will save the Mutant Race from possible extinction (the final shot shows Cyclops getting the cure injected into him as Nightcrawler, Colossus, and Jubilee are among the mutants identified in the line to get cured). If not, the Legacy Virus will turn into a plague that will run rampant across the Earth and the Mutant Race may go extinct (the final shot at a graveyard scene shows that two of its known victims are Colossus and Wolverine).
- X-Force (vol. 1) #18, January 1993
- X-Men (vol. 2) #108
- Uncanny X-Men #390, March 2001
- Astonishing X-Men #4, August 2004
- X-Force (vol. 3) #13