Karadrach was an angel of secrets, and once one of the most loyal servants of Boccob. During the Deity War, he accompanied his master to the Temple of the Mind's Eye in Derenath, where his master seemingly perished in the final battle with Nerull.
Boccob's apparent demise drove Karadrach mad, and he spent the next several years wandering aimlessly through the ruined temple, lost in despair. His despair was broken, however, when he was found by the wizard Tephra. She told him that Boccob had not perished, but become mortal. She further explained that, having claimed his power after his true demise, she was in fact Boccob's rightful successor. In his despair and madness, Karadrach was easily convinced that she spoke the truth, and vowed to serve her as faithfully as he had Boccob. To thank her for helping him find renewed purpose, Karadrach taught her the Words of Creation; Tephra saw further potential in them, however, and asked Karadrach to find a way to modify them into Words of Destruction.
When the Brightstone Heroes led a grand army to Derenath to stop Tephra, Karadrach flew out to demand their immediate and unconditional surrender. When they refused, he commanded Tephra's own armies to stop them before returning to the temple to complete the Words of Destruction. The Challengers of the Unspeakable, along with the dragonborn barbarian Alae, followed him deep into the temple to confront him. He eagerly engaged them in battle, aided by the Words of Destruction, but was struck down. He rose again, however, revealing that Tephra had in fact transformed him into a hideous aberration with black skin, eyes that wept poison, and wings of eldritch blue light. Now entirely consumed by madness and rage, he resumed his attack but was ultimately slain by Kalth.
His remains were buried when the temple collapsed into what became known as Lake Derenath.