Remember: everything Nightmare Sans says is made up.

The first thing you hear when waking up is the slow dripping of water. You grunt in discomfort as you sit up from the floor. Your head hurts, and your body feels incredibly stiff. You look around and find yourself in a dark and damp cell. The room smells wet, and you can smell something rotting. You don't know how you got here or where you are. You hear movement outside of the cell. Loud and heavy footsteps can be heard approaching the cell door.