Born from the Acolytes Rusty Collins and Skids, Sean's genetic make-up readings were magnetically modified by Magneto in order to lure Hank McCoy and unite his fellow mutants, as a rift was forming in his community.
The X-Factor analysis "revealed" that, at maturity, Sean would be able to alter his mutation at will, enabling him to choose himself his powers and therefore, he was part of an evolutionary jump as big from the mutants than was the jump of mutants from humans, and could be the next step, Homo ultima, the ultimate being. While his parents were joyed by the news, McCoy expressed his doubts about what to think of it.
Scanner learned the intel and soon reported it to the Acolytes "Annihilist faction" (in favor of taking Earth from the humans) and to their leader Fabian Cortez who feared that Homo ultima would turn against Homo superior and take Earth for themselves. In the same way, Milan informed Exodus who expressed same concerns.
The two Acolytes factions sought the counsel of Magneto, who let them decide together what should be done, and they agreed on a truce, time to terminate the baby, with less opposition among their ranks.
The Acolytes intercepted McCoy, Skids and Rusty while they were intending to exit the station with a space shuttle. Although Beast and the couple fought bravely, they were unable to prevent Amelia Voght from reluctantly asphyxiating the baby, immediately asking forgiveness for her actions and claiming "it was self-defense".
Once Sean dead, the couple and Beast decided to leave forever the station, while the Acolytes granted gratitude to them, considering that their baby had been a warning for mutantkind and that they will unite to survive this threat. Days later, Colossus decided to leave at his turn, but not before consulting Magnus who admitted his actions, regrets and explained it. Peter left then, warning Magneto about the fact his lies might turn to be true one day.
Powers and Abilities
It is unknown if Sean would have turned to be a mutant and what could had been his powers.