The Quiet Council of Krakoa, the mutant nation where heroes and villains alike are welcomed to start a new life. In truth, Sinister hasn't earned this role because he's trusted; rather, it's simply because he's useful. He's enjoying his new position of prominence, taking advantage of the opportunity to conduct further experiments - potentially unlocking the future of the mutant nation. Naturally, he's doing this in spite of the fact his experiments are strictly prohibited by his fellow mutants.
Kieron Gillen and Lucas Werneck's Immortal X-Men #1 reveals Sinister's latest experiment has allowed him to conquer time itself, in a manner that would make classic Avengers villain Kang the Conqueror envious. Sinister recently learned Moira MacTaggert was a secret mutant with the power of reincarnation; every time she dies, her consciousness returns to the moment of birth, retaining all the knowledge of her previous lives. Sinister had already obtained a copy of Moira's genetic code, and so he has learned how to duplicate the process. He can now experience a lifetime, before committing suicide and returning his consciousness to the moment he granted himself this new power.
It's fascinating to compare Sinister's new abilities with the powers of Kang the Conqueror. Kang can do pretty much the same trick, resetting the timeline around his own consciousness, and indeed he employed this tactic when he waged war against Ultron. But Kang's is actually more limited, because his science-based time travel simply creates branching timelines. In contrast, like mutant and magic-based time travel powers, Sinister's resets the entire timeline - literally erasing everything that has happened. Meanwhile, Sinister has another advantage of Kang, the simplest one of all; the fact nobody knows he can do this. He's kept his latest experiments secret, and is quite enjoying watching how things play out.
There is, however, one crucial difference between Sinister's conquest of time and Kang's. Kang understands the nature of time itself, particularly as regards the so-called "butterfly effect" - the idea that, when you travel back in time, any minor change you make has the potential to ripple on throughout the timeline. Sinister seems to take a more deterministic view of time travel, expecting his consciousness to be the only thing that changes. Unfortunately, even in Immortal X-Men #1 that leads him to make mistakes that could affect the future of Krakoa itself.
Sinister's approach matches with that of the entire mutant community. The X-Men seem willing to push the boundaries of science simply because they exist, blissfully unaware of the consequences. They established the Resurrection Protocols, and nearly killed the avatar of Death itself in the Marvel Universe; they learned how to raid the heart of creation, and unwittingly created an imbalance that allowed the Dread Dormammu to begin a cosmic invasion. No doubt Sinister's conquest of time will have unforeseen consequences in X-Men comics as well.
