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. Buer teaches Natural and Moral Philosophy, Logic, and the virtues of all herbs and plants. He also heals all infirmities, especially of men, and gives good familiars.
Although the etymology of his name is uncertain, curiously there was an ancient city named “Buer” (now Gelsenkirchen) in Westphalia, Germany.
Buer is a president of hell and a demon of the second order who commands 50 legions. His form is that of a five-branched star or wheel, and he moves by rolling himself. He teaches philosophy, logic, and herbal medicine He is also skilled in curing the sick and giving good servants.
Goetia – S. L. MacGregor Mathers (1904) (quoted)
The Tenth Spirit is Buer, a Great President. He appeareth in Sagittary, and that is his shape when the Sun is there. He teaches Philosophy, both Moral and Natural, and the Logic Art, and also the Virtues of all Herbs and Plants. He healeth all distempers in man, and giveth good Familiars. He governeth 50 Legions of Spirits, and his Character of obedience is this, which thou must wear when thou callest him forth unto appearance.