Tower Dungeon manga volume 3 features story and art by Tsutomu Nihei, the creator of Blame!

Level 25 of the Dragon Tower-

Yuva and his companions, having fallen into a trap set by deserters from the Royal Guard, are grievously wounded and on the brink of annihilation. The traitors demand that Eriquo hand over the Dragonbane, a legendary relic they seem to think he secretly carries... But even if they survive this deadly encounter, can our tiny band of adventurers really overcome the dangers of the indomitable labyrinth, defeat the Necromancer, and rescue Princess Ignelia?