A classic X-Men storyline revealed that the ultimate weapon in Marvel's multiverse is the multiverse itself. While the concept of the multiverse has recently been introduced in the MCU through Loki, Spider-Man: No Way Home and the upcoming Doctor Strange in the Multiverse of Madness, it has been a mainstay in the comics for decades. The X-Men in particular have had a lot of timelines in the multiverse, as seen in seminal stories like Age of Apocalypse, Days of Future Past and House of M.

The rules and mechanics of the multiverse can be contradictory. As outlined in Loki, there are certain moments in time known as "nexus points," where history can branch in different directions. An entire branching timeline could be created simply by someone being late for work.  This idea corresponds pretty well with the comics themselves - indeed, they've recently started to incorporate the MCU's jargon too. But, in all the excitement over the multiverse, the MCU has concealed the fact the branched timelines are themselves a formidable weapon.

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This is revealed in 2010's Second Coming event, an X-Men story that sees the mutant race brought to the brink of extinction. After Scarlet Witch de-powers the vast majority of the world's mutants with a powerful curse, Hope Summers - the so-called "Mutant Messiah" - finally returns from the future offering the potential to restart the mutant race. The super-Sentinel Bastion is aware of her coming, though, and he launches a devastating trap using the multiverse as a weapon. Bastion knows there are an infinite number of timelines out there, including one in which the mutant race is successfully rendered extinct by other super-Sentinels, and he figures out how to open a portal to that timeline. He then traps the X-Men in San Francisco with the portal, allowing an unending stream of Nimrod Sentinels to pour out of it in an attempt to wipe out the mutants.

X-Men Nimrod

Bastion has some familiarity with time travel and temporal mechanics, because he himself was created in part from Nimrod Sentinel technology. Marvel Comics has suggested that each timeline has a slightly different resonant frequency, and presumably Bastion uses the Nimrod scraps to locate this particular dystopian timeline. He had then weaponizes it in a remarkable attack that comes close to succeeding. It is only foiled by luck, because Cyclops' son Cable has one time travel jump left in his own device. Beast is able to identify the same resonant frequency and transport Cable and X-Force into the future, where they shut the Nimrods down.

Bastion's strategy is quite remarkable, and it serves to remind fans just how dangerous the multiverse can really be. In Avengers: Infinity War, Doctor Strange glimpse 14 million futures in which Thanos won - 14 million different branched timelines that ended in doom. A time traveler can go one step further, not just seeing the timelines but navigating them, and weaponizing them. The Avengers villain Kang the Conqueror has often done this, but never quite on the scale of Bastion in Second Coming. It remains to be seen whether the MCU will capitalize on the potential of the multiverse, which is revealed so effectively by the X-Men's foes.

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