Selderin Vermth, Archmage of Herun was a powerful archmage of the kingdom of Kingdom of Herun. He build a magnificient tower called the Tower of Oblivion west of Redford and hasn't been seen since the tower locked itself up and the area transformed into a swamp.
A powerful mage, Selderin was tasks with finding a cure for hag children and succeeded.
He later became obsessed with creating high level magic, which led to him trapping himself in his own pocket dimension and not being able to escape.