Umber Hulk

Three words exemplify the umber hulk: big, nasty, and scary. Rarely spawning in the depths of the world, this is not a foe to be underestimated.

Fortunately, they are rather slow. But that is their only weakness: they are incredibly tough and ridiculously resilient, immune to fire, and hit like a sledgehammer. Only the best-geared of adventurers should attempt to do battle with these beasts - to engage them otherwise is folly.

Origin

Umber hulks come are based on Dungeons & Dragons.