Necromancer who killed Mattahar once, and was thought to be dead.
Oreioth first established his domain in a cave outside of Red Larch. Early on, Panapapi Ticcotarp Copperspackle and Mattahar had gone to investigate his dealings, ultimately resulting in the death of Mattahar. Monish Knight and Rinn became involved, ultimately creating the deal with Nalaskur Thaelond that would bring Knight into the Zhentarim in order to restore Mattahar to life, and returned to the cave where they took vengeance on the necromancer, or so they thought.
Oreioth later appeared in Yartar, where he killed an reanimated a gang that made a dock side warehouse their hideout. For reasons unknown, Oreioth had the undead gang abduct twelve people from the riverside region of Yartar. Whatever his plans were, they were thwarted by Mattahar, Papapani, and Rinn when he was forced to surrender to Watch Captain Rizz. As he was being arrested he swore to Matthar that he would kill her again, and once again she would cheat death, only this time it would be in eternal undead servitude to him.