Chaunzaggoroth

Chaunzaggoroth, which Harry Dresden nicknames Chauncy, is a demon from the World Below, the underworld. He first appears in Fool Moon.

Description
Harry Dresden states that Chaunzaggoroth never lied to him.

He has chitinous shoulders, crablike pincers, black eyes, a beaklike nose, and a perfect Oxford accent. He is a popular source of information amongst wizards. He put a pair of wire-rim spectacles on his beak before he started to chat with Harry.

Fool Moon
In Fool Moon, Harry Dresden calls Chaunzaggoroth up into his summoning circle in his basement lab to get information on Harley MacFinn, the Northwest Passage Project and James Douglas Harding III. Chaunzaggoroth insists on getting one of Dresden's names in exchange. And while he's at it, he tries to recruit Harry to his side of things, insisting that Harry's inclination more "like his brethren". He says it would give him status to gain a soul of his caliber into their legions. Because Chaunzaggoroth never lied to Harry, he agrees to the price since he says he has information that could save lives.

He knows three of Dresden's four names: Harry Blackstone Dresden. Before Chaunzaggoroth leaves, he lets drop that he knew Dresden's mother Margaret LeFay but by a different name before her "redemption" and tried to trade more information about her, and the unnatural deaths of her and Dresden's father.