Ganon
Ganon is the alternate form of Ganondorf, King of Evil. He is the demon and antagonist that Link mainly fights through the series. Usually when the triforce is involved Ganon is involved too. He resembles a boar/pig but changes from game to game.
History
Throughout the games, Ganon's intentions haven't changed. Taking the triforce of power or earning it and spreading darkness over Hyrule, And he often kidnaps Zelda in the process. Only his appearance has changed, He is blue and a pig-monster in LoZ while in OoT he is a gerudo and eventually turns into a giant, green monster. Ganon and Ganondorf aren't the same person, Ganondorf is the human/gerudo version while Ganon is the abomination, beast or demon version of Ganondorf.
Trivia
. In The First Game for the NES (The Legend of Zelda) Ganons name was spelled Gannon.