Morgan, Uther's eldest daughter and King Arthur's elder sister, also known as the enchantress Morgan le Fay, is ambitious and wants to take the throne from her younger sister, the Saber King...
Huh? You say she lost her memory after getting hit by a meteorite?
Gawain: "Mother, I'm so moved! I, Gawain, will surely follow your wishes and devote myself to serving the king!"
Agravain: "Mother, I never knew you were so noble and magnanimous. I will do my utmost to support the King of Knights."
Gareth: "Do my brothers have the wrong idea about something?"
Mordred: "...So, am I rebelling or not?"
A story about a different Morgan in the Nasuverse. (Not a transmigration story)