Difficulty raises enemy count/strength and tends to improve rewards (XP/coins). If you’re new, explore the Items Index first, then enable Skuleg when you’re comfortable.
Skuleg is a pure modifier: when equipped, it increases the run’s Difficulty by 7%. Higher Difficulty means denser waves and tougher enemies, which commonly translates into faster XP and coin gain if you can survive.
Requirement: Reach 40% Difficulty in a single run.