What's more, there's a whole new system of "perks" that applies to all the classes in the game. The perk system is a sort of Diablo-style skill tree. Every ten levels, a character can choose another perk, unlocking new bonuses, attacks, and special skills. Even if you never set foot in the Shadowlands, this perk system is almost reason enough to get the expansion pack. It allows some nice new options for differentiating characters as they gain levels.