Gaap

Dictionnaire Infernal – Collin de Plancy (1863) (paraphrased)
Tap/Gaap is a high president and prince of hell, commanding 4 of the principal kings and 60 legions, and as powerful as Byleth. He also has an empire over those demons Amaymon commands. He appears in human form at noon, and is said to intensify the passions of love and hatred, and can transport men to different countries. Earlier necromancers invoked Tap by spells composed by King Solomon, but that is not true, as it was Noah’s son, Cham, who first began evoking evil spirits. The necromancers also offered him libations and holocausts. Tap was made to serve Byleth by composing a book of mathematics. If the exorcist knows of the art of Byleth, Gaap will not cooperate. Another book attributed to the prophets Eli and Elijah states that Gaap can be conjured by virtue of the saints’ names of God listed in the Key of Solomon.

Pseudomonarchia daemonum – Johann Wier (1583) (quoted)

Gaap, alias Tap, a great president and a prince, he appeareth in a meridionall signe, and when he taketh humane shape he is the guide of the foure principall kings, as mightie as Bileth. There were certeine necromancers that offered sacrifices and burnt offerings unto him; and to call him up, they exercised an art, saieng that Salomon the wise made it. Which is false: for it was rather Cham, the sonne of Noah, who after the floud began first to invocate wicked spirits. He invocated Bileth, and made an art in his name, and a booke which is knowne to manie mathematicians. There were burnt offerings and sacrifices made, and gifts given, and much wickednes wrought by the exorcists, who mingled therewithall the holie names of God, the which in that art are everie where expressed. Marie there is an epistle of those names written by Salomon, as also write Helias Hierosolymitanus and Helisæus. It is to be noted, that if anie exorcist have the art of Bileth, and cannot make him stand before him, nor see him, I may not bewraie how and declare the meanes to conteine him, bicause it is abhomination, and for that I have learned nothing from Salomon of his dignitie and office. But yet I will not hide this; to wit, that he maketh a man woonderfull in philosophie and all the liberall sciences: he maketh love, hatred, insensibilitie, invisibilitie, consecration, and consecration of those things that are belonging unto the domination of Amaymon, and delivereth familiars out of the possession of other conjurors, answering truly and perfectly of things present, past, and to come, and transferreth men most speedilie into other nations, he ruleth sixtie six legions, and was of the order of potestats.

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

The Thirty-third Spirit is Gaap. He is a Great President and a Mighty Prince. He appeareth when the Sun is in some of the Southern Signs, in a Human Shape, going before Four Great and Mighty Kings, as if lie were a Guide to conduct them along on their way. His Office is to make men Insensible or Ignorant; as also in Philosophy to make them Knowing, and in all the Liberal Sciences. He can cause Love or Hatred, also he can teach thee to consecrate those things that belong to the Dominion of AMAYMON his King. He can deliver Familiars out of the Custody of other Magicians, and answereth truly and perfectly of things Past, Present, and to Come. He can carry and re-carry men very speedily from one Kingdom to another, at the Will and Pleasure of the Exorcist. He ruleth over 66 Legions of Spirits, and he was of the Order of Potentates. His Seal is this to be made and to be worn as aforesaid, etc.