Utility classes and monsters do primarily other tasks than combat. Usually they buff or debuff opponents, or perform other uses, such as looking for traps or solving social encounters the party needs to overcome. The term is used here to group up many sub-types of archtypes rather than making a multitude of articles for it.
This sort of archtype hails from the PnP RPG of old, with classes like a Rogue or Bard, where their strength do not lie in combat but in either (actual) roleplaying aspects, or physical utility like finding and disarming traps, opening doors and being generally stealthy.
In videogame RPGs, the term can here also be included to classes that specialize in buffing friends or debuffing foes. Primarily popular in Asian MMORPGs, where each class gets very specialized.
The Diablo games don't really have any proper utility class. In Diablo II, the Paladin was pretty close to being a utility, with his Auras and general helpfulness, and the Necromancer with his debuffing curses, but neither was really a "true" utility class, and neither has any other class in the Diablo series been.
With a much wider variety of monsters than classes, some monsters are created solely to make life more difficult for players. Some monsters buff each other or debuff players. Called "Lieutenants" by the D3 Team, they perform a variety of tasks, also including spawning more monsters, resurrecting on top of buff/debufing.
Related articles include:
- Caster - Magic-users. Most utility classes and monsters are casters.
- Ranged - Dealing damage from afar. Most utility classes and monsters are ranged if they deal damage.
- Melee - Close range combat.