Buer is a spirit that appears in the 16th century grimoire Pseudomonarchia Daemonum and its derivatives, where he is described as a Great President of Hell, having fifty legions of demons under his command. He appears when the Sun is in Sagittarius. He teaches natural and moral philosophy, logic, and the virtues of all herbs and plants, and is also capable of healing all infirmities (especially of men) and bestows good familiars.
He has been described as being in the shape of Sagittarius, which is as a centaur with a bow and arrows. Additionally, Louis Le Breton created an illustration of Buer, later engraved by M. Jarrault, depicting the demon as having the head of a lion and five goat legs surrounding his body to walk in every direction. This illustration has been featured on several albums including Morbid Angel's Blessed are the Sick LP, Coil's 'Wrong Eye / Scope' single, Cloven Hoof's 2008 album The Definitive Part One, a 1981 Black Sabbath bootleg LP entitled Buer Album, and the EP Evoco Bestias by the Norwegian avant-garde metal group Fleurety.