Bestia Oscura
Faced with a lack of resources, Cyclops agrees to let Dark Beast work on an 'anti-vaccine' to neutralize Callahan's current mutant 'vaccine', with Warlock monitoring the process of creating the cure to ensure that it does only what Dark Beast says, Dark Beast defining it as a simple airborne virus that will feed the mutant vaccine's virus before it can smother the X-Gene, leaving them free to activate. However, after the anti-vaccine has been dispersed worldwide, it is revealed that Dark Beast, with some help from Mister Sinister, had in fact 'tricked' the X-Men as the serum indeed shuts the virus of the mutant vaccine's and is harmless to those who already had their X-Gene activated, but in the presence of a still inactive X-Gene, it works as a catalyst, becoming lethal for potential mutant children. Dark Beast reasoning that this will 'test' humanity's hatred of mutants by putting them in a position where they will risk their children dying to prevent them becoming mutants. As Dark Beast continues mocking them, Magik executes him with her teleportation discs to send part of Dark Beast into the ceiling, killing him.