Barony

Barony is a 3D, first-person roguelike. The goal of the game is to descend to the bottom of a dark dungeon known as the Devil's Bastion and destroy an undead lich named Baron Herx, who terrorized the peaceful town of Hamlet in life and is now harboring a curse against the land from beyond the grave. To aid you in your quest are friendly humans who have been eeking out a rough life within the dungeon for generations, as well as any friends you can bring with you in real life: Barony is the first of its kind as a first-person roguelike in that it fully supports cooperative multiplayer for up to four players.

Source: The Game Website.