Onslaught is arguably the most powerful supervillian to appear in the Marvel universe. During a major battle between the X-men and Magneto's Brotherhood of Evil Mutants on Magneto's satellite orbitting the Earth, Magneto rips out the adamantium from Wolverine's body, when Logan attacks Magneto who was on the verge of killing his own son, Quicksilver (it is at this point that we realize that Wolverine actually has bone claws beneath the adamantium). Infuriated, Professor Xavier enters Magneto's mind and shuts it down. However, unknown to the Professor, the dark part of Magneto's psyche transfers itself back to Xavier's mind via the telepathic link and remains hidden there. This dark aspect combines with Xavier's frustrations and emotions, his own dark side, and gains sentience and independence. Thus Onslaught is born.
Unknown even to Xavier himself, Onslaught begins engineering events world-wide starting with the liquidation of a Sentinel processing plant and the complete mind-wiping of its staff. Later on, he battles Juggernaut in Canada, knocking him clear across North America. Juggernaut comes to the Phoenix for help because he knew who Onslaught was but couldn't get it out due to a telepathic block. Jean finds out who Onslaught really is and tells Cain to escape.However, Onslaught catches him and rips the Gem of Cyttorak right out of his chest. Thought to be dead, Juggernaut was actually trapped within the Gem where he has to fight the Ruler of Cyttorak.
Onslaught is fascinated by Nate Grey, and through Xavier's encounter with the boy, learns to physically shift himself (and others) in and out of the astral plane physically. Onslaught tries to have Phoenix join him, hoping to use her experience with the Phoenix Force to learn how to gain more power. She declines and when she learned Onslaught's true identity from Juggernaut, she is so shaken that she doesnt formulate a course of action until it is too late.
After the Juggernaut-Phoenix incident, Onslaught reveals himself to the X-Men, who also refused to join him. Apparently, Onslaught is driven by Magneto's quest for mutant domination. More of Magneto's influence is seen in the form of a psi-armor very similar to magneto's costume. Onslaught then battles the X-Men and defeats them. Phoenix then makes the famous X-Traitor recording which intrigues Bishop 100 years later. The x-Men recover but Onslaught lets loose a psionic blast that would have annihilated the X-Men had not Bishop jumped in it's path and absorbed it, thus saving the X-Men and changing his past.Exhaused by his efforts and not yet fully in control of Xavier, Onslaught leaves with Dark Beast who has been posing as the real Beast.
Onslaught next sets his eyes on Franklin Richards, son of Dr.Reed Richards and Susan Storm, whose reality-altering abilities would make Onslaught nearly a god. Onslaught defeats the Fantastic Four and some of the Avengers and makes off with the boy, physically incorporating him into his own structure. He also captured Nate Grey, and with the three most powerful mutants on Earth under his control, creats a citadel in Central Park, and unleashes an electro-magnetic pulse that stops New York cold. Onslaught then reprograms the sentinels he had captured from that factory and sends them out on a rampage against humans, only to be stopped by the X-men.
A major assembly of Marvel heroes takes place as heroes from various parts of the world come forward to battle, what seems to be, the most powerful villian the world has ever seen. Also present is the mind wiped Magneto and Dr.Doom.
During the battle, Xavier is displayed to them, as Onslaught taunted them with his power. At this point, the Mighty Thor bursts through Onslaught and physically removes Xavier from the villain. However, instead of slowing down Onslaught, it turns him into a being of pure psionic energy, no longer bound to its original host.
Onslaught taps into Nate Grey's mind and learns how Apocalypse took over the world. Realizing that neither man nor mutant are worthy to live on Earth, Onslaught decides to obliterate them all. He uses Franklin's awesome power to create a second sun in the sky. Storm and Thor try desperately to minimize the climatic damage. It is at this point that the Hulk asks the Phoenix to shut down his Banner persona, and become a raging monster intent on stomping Onslaught. All this while, all the heroes together had not even been able to scratch Onslaught's armor. The enraged Hulk, with near limitless strength, leaps onto Onslaught and rips off his armor. This results in a blast after which the Hulk and Bruce Banner are seen lying unconcious as two different entities.
Onslaught has now evolved into a being of pure thought. Realizing that matter was needed to contain Onslaught, the heroes start sacrificing themselves to contain the evil that is Onslaught. Thor is the first to leap into the torrent of psionic energy, and when this proves to be insufficient, the rest of the non-mutant heroes join him. Mutant matter would have only enhanced his powers. Thus Onslaught is defeated but seemingly at the cost of most of Marvel's superheroes including the Avengers and the Fantastic Four. However it is later revealed that they are not dead. Instead, Franklin Richards had created pocket universes and transferred them there. It's after many adventures that most of them return to their proper universe.
This is one of Marvel's most spectacular epics, involving almost all of its major superheroes including the X-men,the Avengers,the Fantastic Four,the Hulk and the Mighty Thor. However, a lot of fans allege that this was just a ploy by Marvel to seperate Marvel heroes into various parallel universes, so that they could release more comic series.
Notes
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Nate Grey ( aka
X-Man ) was created in an alternate timeline in which
Apocalypse had conquered North America. He was created from genetic material taken from
Cyclops and
Jean Grey. He is what
Cable would have become without the techo-organic virus.