Grimoire Encyclopædia

The demon Bael appears in the grimoires Book of Incantations, The Discoverie of Witchcraft, The Magical Calendar, The Book of Spirits, The Book of the Office of Spirits, The Grand Grimoire, The Book of Oberon, Pseudomonarchia Daemonum, The Lesser Key of Solomon, Paradise Lost, and Dictionnaire Infernal

From The Lesser Key of Solomon, Crowley/Mathers edition:

Bael

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.