The Nightmare Slime is a Nightmare Mode monster that spawns once the Keeper of Souls has been defeated. It is a black slime that has black mist surrounding it. It inflicts the Nightmare (Debuff). It is very hard to see at night, and will blend in with its surroundings.
- HP: 500
- Damage: 110 (Melee)
- Defense: 50
- 1 gold coin (100%)
- Soul of the Haunted 5-10 (50%)