There's a comic storyline called The Thanos Imperative where an alternate universe, usually called the Cancerverse, invades the main universe. The cancerverse's point of divergence is that when Captain Marvel was about to die of cancer the heroes of Earth made a pact with elder gods from outside the universe to kill the Death. That meant that no one in the cancerverse could ever truly die and became weird lovecraftian abominations instead. It was quite creepy, in a good way. It also got revisited twice, once by Bendis in his early Guardians run (and the less said about that arc, the better), and once again by Jeff Loveness' short-lived 2017 Nova series (which at least got the mechanics of the cancerverse a bit more right).