Final Fantasy XII: Revenant Wings/Espers

Espers are the magical summons used in Final Fantasy XII: Revenant Wings. Also known as "yahri", these little guys can be used to fight in combat.

They come in six elemental types: none, fire, ice/water, thunder, earth, and healing. The esper's type determines what other type it is resistant against and what it is weak against. Excluding the first and last type, each type has a weakness to another. As an example, fire is often weak to ice, but also weak to earth sometimes. Espers also come in combat types. The three combat types are melee, ranged, and flying. These three type work in a rock-paper-scissors fashion, with melee beating ranged, ranged beating flying, and flying beating melee. There is a fourth combat type, and that is healing. Healing units are a subdivision of ranged units, but heal instead of shooting elemental shots.