Elemental

Elementals are the purest living forms of the four basic elements—air, earth, fire, and water—as well as several other, less common elements. They were intelligent, self-aware entities that were made up of the matter of their home plane. They could be summoned to any plane of existence, except the plane of concordance to their element. For example, summoning a fire elemental to the Elemental Plane of Water took more magical power than mortals could conceivably wield.

They are most commonly found in The Abyss.