Berith

Duke Berith of the Ars Goetia. Sneaky and snarky, they tend to mess with people just for amusement, especially with conjurers who believe themselves superior and try to use them. They travel around in a red horse which tends to whisper even while sleeping.

Their artifact and the part of Somnis they're in charge of is Librabis of Gold, the only place of Somnis that uses currency like in the real world. As an artifact, Librabis is a coin.