The X-Men are rapidly approaching the event that will change the Krakoan Era forever, "Fall of X." It promises to be the culmination of the Orchis storyline that has been building up over the last few years, threatening to destroy everything the X-Men have built for mutant-kind. Unfortunately, Marvel's most famous mutants seem less than prepared for the coming storm, and that is largely due to not understanding who their enemy is.
Source:https://www.cbr.com/xmen-fall-of-x-survival-sorcerer-doctor-strange/