"In a cave, far from anything else, there are ancient ruins of old, lost cities. It has a dark secret and no adventurer came back from there. Terrifying creatures roam around, overgrown by dark, slime-like stuff. One creature seems to be made by a ancient group of builders that also built this cities to protect the dimension the dark slime came from. They are hidden underground and can't be killed. The only way to get away from it is the portal that leads to the dark dimension, where nothing is right..."