Its a stone boss by the quest "The Labyrinth"!!!
He attacks in a few different ways. He starts out by punching at flux, causing a fist to emerge from the ground, and setting fire to part of the ground. Hurt him enough and he will summon in minions that spit exploding rocks at you and will pound the ground around him in a big area. There is a major advantage being he cannot move. To start the fight you must step on the golden platform in the chamber if the labyrinth.