This article contains spoilers for Wolverine #6 and X-Force #13.
The X-Men have just unintentionally created a tribe of ninja demons. The Marvel Universe is in a state of flux, largely thanks to the actions of the mutant race. The X-Men have established a mutant nation on the living island of Krakoa, with the United Nations hesitantly recognizing their sovereignty. It's caused geopolitical chaos, and frankly, it increasingly looks as though the Marvel Universe is headed for World War III.
But the ramifications have been greater than the X-Men imagined. Under the mystical principle of "as above, so below," the rise of Krakoa was mirrored by the rise of its twin island Arakko on another plane of existence, called Amenth. Apocalypse unwisely engineered a plan to reunite Krakoa and Arakko by accessing the nexus of all realities, called Otherworld, but he was betrayed. Now ten mutant champions must take part in duels with the Swordbearers of Arakko, with the fate of the Multiverse itself hanging in the balance.
In Benjamin Percy's Wolverine #6 and X-Force #13, Wolverine learns the ramifications are even greater than he feared. The establishment of Krakoa has created rifts between countless different dimensions, and the ancient ninja cult known as the Hand have capitalized upon them. The Hand have always worshiped a monstrous entity called the Beast, but now some of their most ardent believers have been able to access Hell itself. There, they have bonded with the Beast's demonic servants. Essentially, they have reinvented themselves as a cult of ninja demons.
It's true the X-Men could never have anticipated these consequences for their actions. And yet, the fact remains they allowed Apocalypse far too much freedom, barely objected when he conquered one realm of Otherworld in their name and seated Omega mutant Jamie Braddock upon its throne. Apocalypse's plans have evidently changed the nature of reality itself, and in this case, they have unleashed a monstrous new threat upon the world. Wolverine's battle against the Hand is a brief one - Wolverine plunders Hell in order to acquire a Muramasa blade - but these villains are sure to return.
Interestingly, Marvel has already suggested there are other unintended consequences of the establishment of Krakoa. The mutants have conquered death, using a combination of mutant powers and Cerebro technology, and this led to the new-death of the avatar of Death itself. Disturbingly, without the intervention of Jane Foster's Valkyrie, this would have led to the universe becoming a twisted parody of itself, a so-called "Cancerverse." The truth is that the X-Men are currently conducting the grandest experiment in the history of the Marvel Universe, and they have no idea what the implications could be.