Journey through Madness
Dark maniacal mad-wizard
Halaster was one of the most notorious of mad-magicians. He was an incredibly powerful, and devious, level 33 evil mage (compare to Elminster‘s 35 for an idea of power). Like Elminster he was also one of Mystra’s Chosen. It is also said that Halaster remembered any and every slight made against him, and every deed done for him. He was also rather old, though his magic suffered nothing for this. Rather, this led to a growing weariness of life, and he spent many of his years trying to find new monsters, devise new magic and traps, and one of his few consistent delights was watching adventurer’s pit themselves against these obstacles.
As you have likely already guessed, Halaster was the man who made Undermountain into the mad house it is to this day. After finding Undermountain during his adventures, he cleared it out of it’s prior inhabitants, and made the 13 floors comprising it into his own personal magical laboratory. Rumors of his wealth being located on the bottom floor drew adventurers to Undermountain in droves, and Undermountain’s dark reputation was written in their blood.
He is widely accepted to be dead following a major magical experiment gone wrong prior to the SpellPlague.