You`re scared when a skeleton is dancing out of the door and invites you to follow him down into the dungeon.
A long time ago innocent people were imprissioned in the cold, wet dungeon, tortured and then forgotten. The people died a slowly, lonely death. But their souls couldn`t find  peace, so their bodies arised to walk around as undead.
The centuries passed by, the flesh decayed and now there is nothing more left than bones and skeletons.