X-Men by Jonathan Hickman Vol. 3 TP
The X-Men enter the Reign of X!
In the wake of the the Earth-shattering X OF SWORDS, the Captain Commander of Krakoa has made a fateful decision. There's no going back now, for any of the island-nation's residents. But when the Shi'ar Empire asks the X-Men for help, Cyclops joins Storm and Marvel Girl in answering the call! Elsewhere, the door to the Vault swings open at last. But time moves differently in the Vault—and for the beings who emerge, it's been a very, very long time since they entered! And Krakoa's future is at stake when one of mutantkind's greatest threats re-emerges: Nimrod is online!
X-Men (2019) #16-20