First and foremost let me say, spoilers ahead.
Who here has heard of The Lesser Key of Solomon? Perhaps some of you have, but not many people have unless they are really into demonology. The Lesser Key of Solomon is an anonymous book compiled from various sources, and then divided into five sections. The book describes various demons, their ranks within the hierarchy of Hell, as well as what these demons may grants a summoner with, or what curses would befall those who summon one of the spirits written about in this book. Hereditary mentions of these spirits by name, and goes on to even the actually seal found within The Lesser Key of Solomon. Spoiler: the end of the film even goes on to list a few of the things the spirit is known to grant its summoners, all of which can be found pretty much verbatim in the book itself. It is obvious that the creators of this film put a lot of research into the demonic presence their movie revolves around.
Hereditary is not the first film to mention a spirit from the Lesser Key of Solomon, in fact the film The Last Exorcism mentions the spirit Abalam. The problem with The Last Exorcism is that it gets Abalam wrong, where Abalam is portrayed to be this grand Demon scheming to make its way on Earth, the Lesser Key actually mentions Abalam as subordinate to Paimon. Where Hereditary gets it wrong though, is that in summoning Paimon it is expected that Paimon should appear with two spirits, one being Abalam, and the other a spirit named Babel. When Paimon is summoned at the end of the film though there is no mention of Abalam or Babel, at which point if these two did not appear then a sacrifice is needed in order to summon them.
What hereditary did get correct was the symbol used by the cult which summoned Paimon, as well as the description of Paimon’s gifts which are granted to those who summon him. These gifts are listed as being able to teach science, the knowledge of secret things, the knowledge of the Earth, its waters, and the winds, and so on. Paimon is also said to grant familiars to his summoner which are also capable in teaching the summoner all manners of things. What is not mentioned is whether or not Paimon grants riches as stated in the movie, but perhaps that is covered by the “grants lordships, and dignities” mentioned in the book.
For me, the research put into Paimon’s character in the film is one of the things that made the film so engaging. It was refreshing to see the film makers go as far as using accurate symbols, and using the actual description from The Lesser Key of Solomon. I would suggest that if you have not watched this film, that you give it a try, and while your at it, go read The Lesser Key of Solomon.