The Hellmouth is an entrance to hell that manifests as the open jaws of an infernal beast. Depictions of Hellmouths were common during the Middle Ages and Renaissance in manuscripts, and even as dramatic mechanical set pieces in theatrical productions.
Detail of The Mouth of Hell, from the Book of Hours of Catherine of Cleves, 1440
Vision de l’Enfer (Vision of Hell), from Les Visions du chevalier Tondal, 1475
Ludolf of Saxony, Inferno, from Speculum Humanae Salvationis, 1455
Lambert of Saint-Omer, Liber Floridu, 1250 – 1275
Detail of Jugement Dernier – Damnés (Last Judgement – The Damned Souls), 1492
Depiction of The Devil (almost certainly) surrounded by demon names and corresponding sigils from “Le serpent de la Genèse” (The Serpent of Genesis) Volume 2, by Stanislas de Guaita, 1920. Source: Embassy of the Free Mind
The Goetic Circle of Black Evocations and Pacts, to summon Satan for a deal. The circle is formed from human skin, fastened by nails from a coffin of an executed criminal. A parricide’s skull, goat horns, a bat drowned in blood, and the head of a black cat who was fed human flesh must be placed around it. From The Book of Black Magic and Pacts, A.E. Waite, 1910. Source: Embassy of the Free Mind
Illustrations by Martin van Maële from the 1911 edition of the book Satanism and Witchcraft (La Sorcière) by Jules Michelet, first published in 1862. While widely inaccurate, the book was one of the first sympathetic portrayals of the history of witchcraft.
Lucifer is a prince of hell and a demon of the sin Pride. His name became one of Satan’s monikers, but his origins are older than Satan, and go as far back as Greek mythology. It means light-bringer, and is the Latin name for the planet Venus as well. Alessandro Vellutello, 1534⠀
Beelzebub: his name is used as a nickname for the devil, but he’s a demon prince in his own right, known as “Lord of the Flies”. Originally a “false” god of the Philistines, he’s associated with the deadly sin of Gluttony has the power to turn men into animals and vice versa. From Dictionaire Infernal .
Baphomet is a goat headed demon (or deity depending who you ask) that embodies opposing binaries: they’re human and animal, male and female, good and evil. They’re the source of inspiration for the Devil card image in the Rider-Waite Tarot deck, and much Satanic imagery, and are a part of many occult and mystical traditions.⠀
Iblis is the Satan of the Qur’an. He’s the jinn who refused to bow to Adam and thus was cast out of heaven. However, he’s not an opponent to God, he was banished for his disdain for humanity. He has seven hairs on his chin and is blind in one eye. He has a penis on the inner side of his right thigh and the vulva on the other side, and produces his offspring by simply opening and closing his legs together. This is the reason there are so many shayatin (malevolent jinn).