The giant X-Men crossover event "X of Swords" (pronounced "Ten of Swords," like the Roman numeral and the Tarot card) has officially begun and has potentially claimed its first victim. Spoilers ahead for X of Swords: Creation #1 below! In the issue, after Summoner and a wounded Banshee return to Krakoa from Otherworld via The External Gate. This prompts Apocalypse to lead an expedition of mutants through the gate to rescue Unus and to asses the situation. Joining him on the journey was a host of mutants including Havok, Polaris, Beast, Angel, Monet, Siryn, Rictor, Rockslide, and Summoner. Upon arrival, the attack began almost immediately.
After walking through the gate, Apocalypse realized that the four attackers that had laid waste to Otherworld were none other than his original children from thousands of years ago. Though they appeared to show affection for their father, they quickly turned on and attacked him, leaving him mortally wounded. Apocalypse isn't the one seemingly dead though, as Summoner took his name literally and brought the Twilight Sword out (the same weapon used to separate Krakoa and Arakko), slicing into Rockslide and seemingly killing him.
As readers might recall, the two previous issues of the flagship X-Men series set up a relationship between Summoner and Rockslide as they encountered each other on Krakoa and took part in a game. During that game, Summoner made a comment on Rockslide's mutant abilities and his real self, which sets the stage for this moment seen in X of Swords to be a red herring.
Summoner tells Rockslide in X-Men #12: "Your external form is simply a rocky shell -- armor of stone -- that protects and hides the energy self that is the real you." This quote alone already gives Marvel the opportunity to resurrect Rockslide almost immediately. Considering the lengthy process by which X-Men resurrection takes place on Krakoa though, and the revelation that Rockslide's true self is made of energy and not a physical body, could throw a wrinkle in this.
The X of Swords crossover continues on from now through November though, with the next seven chapters all being released over the course of the next three weeks. X-Factor #4, arriving on September 30, will be Chapter 2 of the event, with Wolverine #6, X-Force #13. and Marauders #13 acting as the next three chapters on October 7th. The first chapter, X of Swords: Creation #1, is on sale now. You can find the full checklist for the event below.