Seth

Seth is a healer or medical man whom ran the religious group that previously occupied The Abandoned Temple to Ilmater and held Amaru (The Forever Man) captive.

History
Based on the letters found in the ruins of the temple it is revealed that Seth was a healer tasked with helping to find a cure for a strange plague that was sweeping through Waterdeep at the time. His first attempts yielded no results until he found Amaru who shared his secret of immortality with him. Together the pair find that ingesting Amaru's blood has several benefits. After curing Seth's family however, Seth started to see the possibility for making a profit from selling their cure, justifying it by suggesting the money could be used to maintain the temple. Amaru didn't want to make money off the sick and so tried to leave. Desperate, Seth trapped Amaru in a hidden room in the temple and began harvesting his blood against his will. This process continued until Seth eventually died of natural causes. Leaving Amaru abandoned.