Preceptor Miriam is a recurring Invader Introduced in Elden Ring. You don't need to defeat him to complete the game. Preceptor Miriam was one of the sorcerers that served the Carian Royals.

The Miriam’s Vanishing is a Sorcery introduced in Elden Ring: Shadow of the Erdtree. Sorcery of a preceptor who served the Carian royal family. Used to conceal oneself in a glintstone haze ...