Trabak

Trabak is the real main villain of The Legend of Zelda: Eternal Shadow. He pretends to help out Link for the first half of the game, until he betrays Link and Midna after Link defeats the boss of the Bluesea Temple. He captures them and tosses them into Jailbrig Cavern, the fourth dungeon of the game. They meet up with him and fight. Link defeats Trabak and he retreats for now. He returns before the Chillhot Mountain boss battle, as he brings the monster Blizzburn back to life. Link manages to defeat Blizzburn and takes one of the 8 Rainbow Crystals. You don't hear of Trabak until the beginning of the eighth dungeon, the World of Shadows. It is revealed before the boss fight, that HE is the Eternal Shadow that Ganondorf unleashed upon Hyrule. He transforms into his true form, the Trabanator. Despite his new powers, Link manages to defeat him and Trabak retreats to Ganondorf's Palace. Link confronts Ganondorf and defeats him. Ganondorf was about to be defeated once and for all, but Trabak comes out of nowhere and possesses Ganondorf and the union produces Ganbak. Despite the evil fusion, Link defeats it, destroys Trabak, and rescues Zelda.