Silverbones

Now that Markus is an S-tier adventurer, he thinks he's at the top of the world. It's a nice delusion while it lasts. He's contacted by a mysterious organization of hyper-powerful beings called the Silverbones, whose purpose is half and half: protect the world, and destroy the world. Markus is invited to try out for this secret, deadly organization.
To become a Silverbones member, Markus must pass a series of challenges and earn fifteen votes from among the seventeen current members. With Alice still missing and the world still falling prey to portals, Markus must face himself and make the ultimate decision to save the world... if he can.