Ghost Zelda is a friendly undead Character from The Legend of Zelda: Spirit Tracks.
In The Legend of Zelda: Spirit Tracks, Zelda and Link are riding the latter's train to investigate the Tower of Spirits when the railroad mysteriously vanishes into thin air. Trying to keep control of the vehicle, Link uses an emergency brake causing the locomotive to fall over on the grass. This was the work of Zelda's attendant, Chancellor Cole and his right-hand man, Byrne. They then break apart the Tower of Spirits, summon the Demon Train and finally kill Zelda, taking her body. Link later wakes up in the castle after regaining conciousness, where he discovers Zelda's Ghost searching for help. It is soon discovered that only Link is the only human able to see her, for some reason. The pair find a footpath to the base of the Tower of Spirits, and in said tower, they meet Anjean, a member of a magical race known as Lokomos, and servant to the Spirits of Hyrule. Anjean tells them that Malladus, the Demon King intends to resurrect himself through Zelda's body. Anjean reveals that the Spirit Tracks are disappearing and that the hold on Malladus is weakening. Anjean lets them take the Spirit Train, as the other train had been derailed. Link and Zelda go to restore the Spirit Tracks.
The two embark on the quest and meet the other Lokomos, who are sages. Link plays a duet with each of them to unlock more Spirit Tracks. Link and Zelda team up in the Tower of Spirits, with Zelda possessing a Phantom Guardian. When they climb to the top of the Tower of Spirits, Byrne stalls them from getting to the top. They make it up just in time for Malladus to be fully resurrected. Malladus blasts Byrne with magical energy as Cole reveals that Byrne had been used. Malladus and Cole then fly away on the Demon Train. After that, Link and Zelda journey to the Sand Temple and retrieve the Bow of Light, which grants them access to a secret entrance at the top of the Tower of Spirits.
Link and Zelda find the Compass of Light at the top of the Tower of Spirits. The Compass of Light guides them to the Dark Realm, where Malladus and Cole are aboard the Demon Train. Anjean and Byrne stay on the Spirit Train while Link and Zelda (in Phantom Armor) confront Malladus and Cole. After Link shoots Malladus, who was in possession of Zelda's body, with a Light Arrow, Malladus is forced out of Zelda's body. Zelda flies over to reclaim her physical form, but she passes through it. As Malladus rushes back to reclaim it, Byrne creates a shield and tells Zelda that she does have a sacred power and to call out to it. Zelda reenters her body, but Byrne is killed by Malladus' magic. Malladus possesses Cole and plans to destroy the world. Link and Zelda weaken Malladus with a song and defeat him once and for all.