This undead serpentfolk wizard came up out of the ground at the end of the Lost City book and set up shop on the old haunted house in the artisan district.
When the PC’s met up with him he cast Black Tentacles on the tightly packed party. The two characters with the lowest fort saves were the only ones to get out (Nig and Jo). They wound up killing this guy and all his little undead guys without too much trouble, by casting two more Black Tentacles on him in addition to lightening, bombs and arrows.
This fight goes to show how even without the three fighters, the party is still over powered for this adventure.