Dragon Star, Goblin Moon
Tarnhem is a balor and the former ruler of the 489th layer of the Abyss. Tarnhem stands twelve feet tall with dark red skin, leathery wings, and clawed hands and feet. His face is fanged and demonic.
Tarnhem’s Abyssal layer, called Noisome Vale, is covered in volcanic vents and cut by a ravine full of writhing worms. The worms inhale the acidic gas that suffuses the layer and exhale breathable air, which allows mortals to survive the atmosphere as long as they remain near the ravine of worms. Tarnhem’s manor is on the edge of the ravine, but the constant whisperings of the worms can be maddening. His manor is still maintained by Tarnhem’s servants, though Tarnhem himself hasn’t been seen since his disappearance over 800 years ago. Currently, the marilith Kaon claims rulership of the layer in Tarnhem’s name by keeping control of the Seat of Grubs, though this claim is known to be spurious by all who dwell in the manor.
Long ago, Tarnhem was summoned by a conjurer who could not hope to control him. After devouring the wizard, the demon raped his servant girl, impregnating her with the cambion boy that would later be named Acererak, The Devourer.
When Acererak sought to transform himself into a lich, one of the prerequisites for the ritual was that he knew the true name of his fiendish father. After much arcane research, the cambion learned the demon’s true name, Maasgheldur, and used it to bind him into servitude. He has never forgiven Tarnhem for the fiend’s treatment of his mother, and took glee in enslaving his mother’s rapist. Tarnhem is rumored to be imprisoned in a crystal vessel hidden somewhere in the depths of the Abyss.
Through his mastery of Tarnhem, Acererak controls a small cadre of demons, who he forced to help him build his trap-laden dungeons. Under the duress of Acererak’s command, these former servants of Tarnhem maintain vigilance over the Tomb of Horrors and his other works to this day.