Marchosias appears as a she-wolf with the wings of a griffin and a serpent's tail, vomiting fire, and then takes human form. Broken into parts, the description uses nothing that a seventeenth-century reader would have found unfamiliar.
The catalogue's creatures are assembled from a small stock: lion, wolf, bear, bull, ram, calf, horse, dromedary, leopard, raven, thrush, stork, peacock, crocodile, viper, serpent, dragon, griffin. Bodies are combined, three heads is the commonest formula, used for Bael, Aim, Asmoday and Balam, and mounts are specified: a bear, a black horse, a pale horse, an infernal dragon, a black wolf, a viper. Several entries add a bird on the fist, which is falconry, and several add trumpets sounding before the spirit, which is a herald announcing a great person.
The vocabulary is that of the bestiary tradition and of heraldry, both of which were part of ordinary visual literacy. A griffin's wings and a serpent's tail are heraldic attributes; a beast that appears in one form and then another on command is a standard bestiary and folktale move. There is nothing exotic in the imagery at all, once its sources are named.
One further point of provenance is worth making because the images are so widely reproduced. The pictures of Goetic spirits that circulate today, Marchosias as a winged wolf, Bael with his three heads, Andras on his wolf, are largely the engravings Louis Le Breton made for the 1863 edition of Collin de Plancy's Dictionnaire Infernal. They are nineteenth-century French book illustration. They are not in the Lemegeton, whose only images are the seals.