Norma Goodfellow

The unnamed Master of Saber is the Master of Saber in the Subcategory Holy Grail War of Fate/Labyrinth before Manaka Sajyou possesses her body.

Fate/Labyrinth
The instant she summons Saber, the Master of Saber is possessed by Manaka Sajyou and spends the remaineder of the war as a subconscious viewer through Manaka's eyes.