Fan CastingFire Emblem 3 Houses

Description of Lady Rhea:

Archbishop of the Church of Seiros. She is in reality the 1000+ year old Saint Seiros Herself, and daughter of Sothis. She has the ability to transform into a mighty white dragon. Though initially suspicious Byleth comes look to Rhea like family (Rhea was like a mother to Byleth's mother Sitri, and Byleth is linked to Rhea's mother Sothis). She vanished at the start of the war, and is later found to be a prisoner in the empire, weakened by her imprisonment she steps down as leader of the Church and names Byleth as the New Archbishop.