Several major changes are apparent in Diablo III; compared to Diablo II, each character class has more skills available to use (Diablo II had only a maximum of '''thirty''' skills per character). Also notable, is that Diablo III separates a character's skills into '''Tiers''' - some skills that exist on higher Tiers require the learning of a skill in a lower Tier; likewise, a higher Tier may require a certain number of skill points spent in a lower Tier to access any skills in it. Each Tier also is the same Tier across each skill tree. So far, there appears to be a maximum of exactly '''six''' Tiers for any given skill tree. (Tier I is level 1 to 4, ; Tier II begins at level 5, ; Tier III begins at level 10, ; Tier IV begins at level 15, ; Tier V begins at level 20, ; and Tier VI is level 25 and onwards).