Alessa

From BorgoWiki

Alessa was an elven archmage from the city of Moonfall. After the horrors wrought on the city by one of the Jin Jiroshes, Alessa studied the arts of elven high magic in order to transcend her mortal form to become a Baelnorn. She failed, and became a Lich. To protect the realm from the evil creature she would become, she had her protégé seal her away inside of her own phylactory.