Bael

Bael, the first spirit, is a king who appears in various shapes - such as a cat, toad, man or all these forms at once.

Dictionnaire Infernal - Collin de Plancy (1863) (paraphrased)

According to the le Grand Grimoire, Bael is the head of the infernal powers. He is also the first demon listed in Wierus’ Pseudomonarchia daemonum. According to Wierus, Bael is first king of hell with estates in the East. He has three heads: a toad, a man, and a cat. He also speaks in a raucous, but well formed voice, and commands 66 legions. Bael teaches the art of invisibility, and may be the equivalent of Baal.

Pseudomonarchia daemonum - Johann Wier (1583) (quoted)

Baell - Their first and principall king (which is of the power of the east) is called Baell who when he is conjured up, appeareth with three heads; the first, like a tode; the second, like a man; the third, like a cat. He speaketh with a hoarse voice, he maketh a man go invisible [and wise], he hath under his obedience and rule sixtie and six legions of divels.

Goetia - S. L. MacGregor Mathers (1904) (quoted)

The First Principal Spirit is a King ruling in the East, called Bael. He maketh thee to go Invisible. He ruleth over 66 Legions of Infernal Spirits. He appeareth in divers shapes, sometimes like a Cat, sometimes like a Toad, and sometimes like a Man, and sometimes all these forms at once. He speaketh hoarsely. This is his character which is used to be worn as a Lamen before him who calleth him forth, or else he will not do thee homage.