The X-Men corner of the Marvel Universe is unlike any other. The one thing that links most of the heroes and villains in the X-books is that they're all mutants. With a single explanation of where everyone's power comes from, this means plenty of characters can be introduced quickly without a lot of time spent on their backstories.
Source：https://www.cbr.com/x-men-villains-best-worst-first-impressions/
