Ganondorf's Steed

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

The Legend of Zelda: Ocarina of Time
During Link's dream about things to come, Ganondorf is seen atop his steed. This dream later comes true when Link is confronted by Ganondorf on his steed outside of Hyrule Castle Town. The horse is very large, and looks somewhat 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. In the German translation of the game, the same Gossip Stone states that the steed came from Hell, though this is most likely a case of artistic license.

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 outside of a flash back scene.

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 and is vaguely implied to be dead, it is possible that he had perished sometime in the past seven years, and that his ghost is the horse ridden by Phantom Ganon. This is supported by the fact that as an adult Link 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. Due to this, it is assumed that either Ganondorf's Steed had passed away during the seven years Link was sealed in the Sacred Realm, or Epona is superior to the black stallion. If it is true that Ganondorf's original horse is dead, then it would seem that he did find a very similar horse, in color and size, for his fight in Twilight Princess.