Tamamo-no-Mae

A beautiful woman who served Emperor Toba said to be the disguised figure of the white-faced, nine-tailed fox. Her childhood name was Misukume. Working in the palace since she was 18 years old, she later became a court lady of Emperor Toba under the name of Tamamo-no-Mae. She was said to have gradually gained the favor of Emperor Toba with her beauty and extensive knowledge.

In reality, she is a soul that branched off from Amaterasu and her true identity is not that of a nine-tailed fox, but rather is treated as one of the facets of said goddess. It is wrong to categorize her as a Heroic Spirit though she manifests as such because she wished to "become a good wife"

The Tamamo Nine are a group of nine Heroic Spirits consisting of Tamamo-no-Mae and eight Alter Egos of her.

In Fate/Extra
She is a Caster-class Servant. It is revealed that she was once the Servant of the game's final antagonist Twice H. Pieceman before he gained Saver. Twice kept losing and respawning in the war and, eventually, lost Caster.