WARNING: The following contains spoilers for X-Men #15 by Jonathan Hickman, Mahmud Asrar, Sunny Gho, VC’s Clayton Cowles, and Tom Muller; Excalibur #15 by Tini Howard, Mahmud Asrar & Stefano Caselli, Sunny Gho & Rachelle Rosenberg, VC’s Clayton Cowles, and Tom Muller; and X of Swords: Destruction #1 by Jonathon Hickman & Tini Howard, Pepe Larraz, Marte Gracia, VC’s Clayton Cowles, and Tom Muller.
The X-Men have always been quick to work with their rivals. Magento was the team's most dangerous enemy for nearly two decades before he joined them. The X-Men invited two more villains, Mister Sinister and Apocalypse, into the fold during the formation of Krakoa as a nation.
Although both helped shape the early days of Krakoa, they took very different paths during the "X of Swords" crossover.
Mister Sinister, Doctor Nathaniel Essex, committed one of the vilest acts in the history of the X-Men when he perpetrated the Mutant Massacre, as his Marauders killed as many Morlocks as they could. Sinister also personally interfered in the lives of a number of mutants, most notably the Summers family. Sinister took advantage of Cyclops’ time in the hospital after the plane crash that killed his mother and activated his latent powers, experimenting on the mutant. Later on, he created Madelyne Pryor, a clone of Jean Grey and the future Goblin Queen, to seduce Cyclops after Jean’s death.
Apocalypse’s crimes against his fellow mutants mostly stem from his want of having Four Horseman: War, Famine, Pestilence, and Death. Apocalypse, also known as En Sabah Nur, both biologically and mechanically alters and brainwashes mutants like the X-Men's Archangel into his deadly, loyal Horsemen. Apocalypse’s rationale is that if he doesn’t test mutantkind, they’ll remain weak, never rising up to take their rightful mantle as the stewards of the Earth.
"X of Swords" began when Apocalypse opened a gate to find his long lost children. The original Four Horsemen decimate him, but while he’s healing he reveals that his wife, Genesis, and their children left him to fight the war in Arakko and knew that this fight would come to the Earth. While they were gone, he had to raise an army that could defeat the hordes in order to save both worlds.
When the time finally did come, he prepared ten champions for the tournament and led them into battle. He showed a tenderness that he’d never shown before, especially during the wedding between Cypher and Bei the Blood Moon in Excalibur #14 by Tini Howard and Mahmud Asrar, advising Doug to accept the vows. While that hinted at an emotional evolution in him, he would soon truly showcase his growth.
The X of Swords tournament came down to one final battle: Apocalypse against his wife, Genesis, to the death. He eventually manages to disarm her but when he has the opportunity to kill her he refuses. It’s a minor moment of redemption, with an even grander one to follow. Genesis puts on the Annihilation mask and calls for her army to invade Otherworld and raze Krakoa, breaking the rules of the tournament. Apocalypse takes the mask from her and puts it on. It’s the apotheosis that Apocalypse has been seeking, but he ultimately rejects it. By wearing the mask he’s become the leader of an unstoppable army, but he uses all of his power to surrender. In effect, he chooses a life with Genesis over a life of conquering and destruction. After so many years of fighting, Apocalypse chooses to stop.
Mr. Sinister seems to be on a similar path X of Swords starts as he’s told that he’s going to lead the Hellions on a suicide mission to steal the swords of Arakko’s champions. It’s not the first time that Sinister deceives the Quiet Council, but before he goes, he makes a pit stop at his illegal clone lab to make sure that if he does die another clone is ready to take over his duties. Then the team disappeared for a few weeks until they reappeared in Hellions #6 by Zeb Wells and Carmen Carnero. He hasn’t been leading them to help the Champions of Krakoa at all. He releases a case of Genetic Collection Drones and leaves his team to fight the Locus Vile alone.
That Sinister's body is destroyed, but when Psylocke and the surviving Hellions arrive in Krakoa, the clone he activated earlier slaughters them at the gate. As he kills them, he sings before putting on a serious face and playing the victim when he comes before the Quiet Council.
Unlike Apocalypse, Mr. Sinister has chosen to remain evil. The contrast of the two stories reveals one of the themes of "X of Swords," a tournament that’s been full of growth for the champions but one that's only brought change to those who really want it.