Supper of Beasts is a cuisine served during the rite of confabulation of Sabbath's Black Mass gathering. The food is described in detail in Monster Girl Encyclopedia World Guide III: Sabbath Grimoire book.
Book Entry
We can say that the extravagant cuisine lining the tables during the rite of confabulation is meant to pave the way for the “rite of depravity” which is to come later. The “supper of beasts” that is prepared for participants of the feast of pleasure known as black mass contains ample amounts of extremely nutritious ingredients such as mamono realm beast meat dripping with juice and thick, rich cheese.
As suggested by the name “beast”, these dishes are made only with enhancing male stamina and redirecting it towards the witches in mind. Of the nutrition that is obtained from eating this food, only a miniscule amount is stored for building up the body, and almost all of it is employed to produce semen and mana. Furthermore, it has the property of being absorbed immediately as soon as it is taken into the body, and the nutrition obtained from eating a “supper of beasts” is thus instantly converted into “stamina”. Therefore, it is suitable to eat as much as one pleases without there being any concern of health issues or obesity resulting from overeating, and that's why it is possible to push the envelope of gluttony during black mass.
However, the “stamina” gained from eating this food can only be expended through ejaculation. In the case of a man, the more he eats, the urge to ejaculate will soar limitlessly higher. Even if only the regular portion for an adult male is consumed, the urge won't settle with just one or two ejaculations. If he's feasted to the point that it could be considered surfeit, then he'll end up having to repeatedly ejaculate a countless number of times so that he'll continuously pour semen into witches throughout the duration of black mass.
Witches will actively recommend the “supper of beasts” and try to get their onii-chan to eat so they can get ravaged by him later on during the “rite of depravity”. While the results may differ, the way that witches can be seen going “ahn” in a sweet voice to get their onii-chan to open his mouth and eat the food every time during the rite of confabulation is reminiscent of the witches of the past era who according to folklore are said to have fed humans to fatten them up before eating them.[1]