Ganondorf's Steed

Ganondorf's Steed is a recurring character in the Legend of Zelda series. He is a giant black horse covered in armor, who belongs to none other than the Evil King, Ganondorf.

The Legend of Zelda: Ocarina of Time
When Link is a child, Ganondorf can often be seen roaming Hyrule atop his devoted steed. The horse is very large, and looks some-what demonic. A Gossip Stone in the game, reveals that Ganondorf's Steed is a Gerudo stallion, leading to the possibility that he could be one of a massive breed.

When Link is an adult, he has the chance to win Epona at Lon Lon Ranch, by beating Ingo in two horse races. When he accomplishes this, Ingo reveals to Link that he had planned to give Epona to Ganondorf as a gift. This probably means one of two things. Either Ganondorf's Steed had passed away during the seven years Link was sealed in the Sacred Realm, or Epona is superior to that of the black stallion.

The Legend of Zelda: Twilight Princess
As part of the final boss battle, Link is forced to fight Ganondorf while he is riding his horse. It is unknown if this is the same horse as in Ocarina of Time, but it is the only time he appears in the game.

Theory
In Ocarina of Time, Link encounters Phantom Ganon in the Forest Temple. The antagonist's phantom rides atop an identical horse to Ganondorf's. Because Ganondorf's Steed is never mentioned in the adult portion of the game, it is possible that he had perished sometime in the past seven years, and that his ghost is the horse riden by Phantom Ganon.