WARNING: The following contains spoilers for Hellions #11 by Zeb Wells, Stephen Segovia, David Curiel & VC's Ariana Maher, on sale now.
Recently, it's appeared that Arcade has been working against Krakoa, even getting the better of Mister Sinister and capturing him. But in reality, Mister Sinister and Mastermind have secretly been working together, allowing Sinister to create his own secret cloning farm under Arcade's nose.
And by doing this in Hellions #11, Sinister just gained some autonomy away from Krakoa and may have helped set the stage for one of the most frightening timelines from Powers of X.
When Krakoa was formed, Moira X was wary of an alliance with Mister Sinister. She had plenty of reason to, considering one of the previous timelines she lived through had gone off the rails when some of the Chimeras created by Mister Sinister -- genetically manipulated fusions of mutant DNA into a new being -- went wild. This resulted in widespread chaos and death, eventually forcing most of what remained of the mutant population to flee into the depths of space. This timeline is one of the most potentially dangerous of all the timelines Moira X lived through -- and one that's been quietly already teased in the core Marvel Universe, with Bishop theorizing on the potential of fusing mutant DNA together and Abigail Brand's backup plan for the Five in King In Black requiring a similar deep-dive into the depths of space.
However, Mister Sinister may have just pushed Krakoa further down that path. When Sinister was allowed to become a part of Krakoa, he was given a certain amount of power. However, he was forced to constrain himself to specific laws and requirements of Krakoa. That no longer seems to be the case, however. In Hellions #9 and #10, it appeared that Mister Sinister and his Hellions had been caught unaware by Mastermind and captured within one of his Murder-Worlds. Arcade demanded a cloning farm be provided to him by Sinister, allowing him to create mutant killers for his designs. But it turns out this was a long-con by Sinister and Mastermind. While it initially appeared that Mastermind was willing to work for Arcade for the safety of his daughter's life, Mastermind has been quietly working with Sinister all along.
Sinister wanted the chance to get off Krakoa with less suspicion that may have been afforded to him otherwise. Arcade's cloning farm is actually Sinister's, with Mastermind using his powers to keep Arcade under their control. Now, Sinister has a secret base to conduct his more dangerous experiments with, giving him a place to build fearsome new forces while ignoring any kind of moral constraints that Krakoa would bring against him. This could allow Sinister the perfect place to build his first generation of Chimera mutants, further setting up Krakoa for ruin. He even allows it to remain disguised as a Muder-World -- giving him the ability to inform the Council of its overt purpose and have it destroyed before anyone could ever try to properly investigate it if he feels it's close to being uncovered.
The only people who seem aware of the location and its true potential are Mister Sinister, Mastermind, Lady Mastermind and Psylocke -- who was able to fight her way through Mastermind's illusions and learn the truth. To ensure her silence, Mister Sinister arranges for her daughter's consciousness -- which was rescued by Psylocke in Fallen Angels and remains in Sinister's hands -- to be transferred to the Murder-World location. If Murder-World is destroyed, Psylocke loses her daughter all over again. It's a terrifying advantage for Sinister to gain, setting him to operate outside of Krakoa's interests and towards his own goals. Considering he's Mister Sinister, it's unlikely that interests will be anything positive. But by taking this step forward, Sinister might even be setting up a genuinely terrible future for the mutant race.