The old kingdom of the Dwarves. In fact, one part recreates the Tomb of Balin scene, but with a ton of zombies instead of goblins.
When running away from the guards in the Southrealm Temple, you enter a cave. Inside the cave you come across this massive thing laying spider eggs. As you progress, suddenly there's a loud crashing sound and you realize that the thing is following you. You seem to escape it for a moment...Then it eats you. You survive. And no other reference is made to it.