- "They say that the horse Ganondorf rides is a solid black Gerudo stallion."
- — Gossip Stone
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 localization of the game, the same Gossip Stone states that the steed came from Hell, though this is most likely a case of artistic license (and possibly meant to imply that it is the same horse used by Phantom Ganon).
Phantom Ganon rides a similar steed, which is either a doppelganger created by Ganondorf or was transformed by Ganondorf's magic to serve as Phantom Ganon's steed.
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.
Though Ganondorf's Steed itself does not appear in the game, located in the corner of Romani and Cremia's bedroom near Romani's bed there is a doll in the form of Ganondorf's Steed. It is one of the many Easter Eggs added to the 3DS remake.
Ganondorf can briefly be seen riding his horse during his battle intro cutscene. In the intro he rides to the battlefield on his horse and after arriving at his destination he gathers his dark magic and levitates off his horse while laughing, at which Ganondorf's "Demon King" title and name appear on screen. Unlike Link's horse Epona, Ganondorf's does not use his horse fight. It only appears in Ganondorf's intro cutscene.
Phantom Ganon's Steed
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.
Another possibility is that after creating Phantom Ganon, Ganondorf used his magic to transform the horse into an evil spirit or demonic being to serve his doppelganger.
However its also possible that Phantom Ganon's Steed is simply the steed's doppelganger that was created along with Phantom Ganon.
Its also possible that the horse is sill alive and simply never encountered by Adult Link, similar to the white horse used by Impa and Zelda as they flee from Ganondorf (which only appears briefly and is never seen anywhere in Hyrule outside of cutscenes) following his attack on Hyrule Castle.
If it is true that Ganondorf's original horse is dead in the Adult Timeline, then it would seem that in the Child Timeline Ganondorf ether somehow prevented its death (possibly transforming or resurrecting it with his magic) or found another steed identical to it. It is also possible that he was riding its ghost and/or demonic spirit, which would explain the ghostly attack he used in battle. Another possibility is that Ganondorf may have resurrected or transformed it into a demonic entity.
Gerudo Stallion of Twilight
Another possibility is the one that appears in Twilight Princess could be either the reincarnation or offspring (descendant or relative) the one from Ocarina of Time.
Ganondorf's original steed may have been killed either after or during Ganondorf's capture and imprisonment in the Arbiter's Grounds.