It Lurks Below has four difficulty levels: Normal, Nightmare, Hell, Inferno. As with Diablo and other games of the ARPG genre, each subsequent difficulty ramps up the monsters levels and reduces your resistances.
Normal difficulty[]
- Monster level 1-35
Nightmare difficulty[]
- Monster level 35-65
- All monsters possess deadly Monster Modifiers
- On Nightmare, players suffer from the Nightmare difficulty debuff:
-50 to all resists
Hell difficulty[]
- Monster level 65-90
- All monsters possess deadly Monster Modifiers
- On Hell, players suffer from the Hell difficulty debuff:
-100 to all resists
Inferno difficulty[]
- Monster level 90-110
- All monsters possess deadly Monster Modifiers
- On Inferno, players suffer from the Inferno difficulty debuff:
-150 to all resists
World Books[]
Sold at 
Wizard of Space and Time .
They allow you to reset the world below Dirt Layer and Badlands, spawning in new monsters.
- Don't worry about your buildings disappearing, only the areas below Dirt Layer and Badlands get respawned
- The books get re-stocked every in-game day (midnight)
- Be careful when you first enter a higher difficulty, it sure is a step-up
Normal World Book
- Resets the world on Normal difficulty
- Costs 100
gold
- Resets the world on Nightmare difficulty
- Available for purchase at level 25
- Costs 1000 gold
- Resets the world on Hell difficulty
- Available for purchase at level 55
- Costs 5000 gold
- Resets the world on Inferno difficulty
- Available for purchase at level 80
- Costs 10000 gold
