"Greetings Avengers... I am here to warn you that a catastrophe is about to befall this timeline and I need your help to stop it! ...wait ...are you the Champions of the Omniverse?"
"Who are they?" Firenado asks.
"It is what your team will be known as in your personal future," Immortus states grandly, "those of you who survive."
Immortus goes on to explain that a series of events will lead to the Earth being destroyed in nuclear fire when solar flares detonate ever reactor on the planet. To avoid this fate, Immortus has pulled the Avengers/Champions and the Avengers Mansion into Limbo for protection and so that he can send them out to save the time-stream. Agreeing to help, the team are told that a young man is about to encounter an alien device in 1960 that will increase his intelligence, but cause a tumor that will eventually kill him. The man will grow up to invent a brilliant, but flawed coolant system for nuclear power generation which will propagate the technology over the globe.