In the Final Fantasy series, Unicorn is a summon who originated in Final Fantasy VI for the SNES, and later went on to appear in a multitude of spinoff titles (most notably the Chocobo series of games).
In order to get Unicorn, the player does not have to fight the mythical horse creature, but will rather get it automatically by entering the Magitek Research Facility. It's ability, titled Heal Horn, will cause it to use Remedy on the entire cast of characters. In the Game Boy Advance remake the name of the ability is Healing Horn.
Unicorn also appeared in Final Fantasy Fables: Chocobo Tales, and four other PlayStation 1 exclusive titles (Final Fantasy Tactics, Chocobo's Mystery Dungeon, Chocobo Mystery Dungeon 2, and Chocobo Racing).