Met a unique in the infinite dungeon, Grgglck, the devouring darkness, that has 500% resist to all (and 32% (extra ?) to nature)!!!
I don't know if it is a bug, but I really wonder how such a beast can be killed
Not really. He just ran out of a vault.
I tried several means to kill him, but all dealt 0 damage. So I just skipped him and escaped to the next level....