Maerlyn

Maerlyn was a human apprentice who specialized in absorption of arcane powers, memories, and souls.

History
It wass rumored that Halaster Blackcloak took her on due to her resistance to the Spellplague that he somehow knew was coming. She was consumed by her own experiments when she summoned a lifedrinker specter that slowly drained away her memories and life-force. She existed only as a ghost for a long period of time and was tortured by said specter until "freed" by adventurers.