From the Lemegeton (Keys of Solomon):
The 31 spirit in order, [as Salomon saith,] is named Foras, he is a mighty great president & appeareth in ye form of a strong man, in humane shape he can give ye understanding to men how they may know ye vertues of all hearbs & precious stones, & [he] teacheth them ye art [of] Logick & Ethicks in All their partes if desired, he maketh men Invisible, witty, Eloquent & to live Long; he [can] discover Treasures and recover Things lost, & he ruleth over 29 Legions of spirits, his seale or Character is thus to be made & worne as a Lamen.So he is a powerful demon who controls 29 legions. He is also one of the knowledgeable demons so it is likely he is summoned for his knowledge of herbs and medicine. It is claimed he can teach men the secrets of longevity.
Up next is a demon that is often confused with Foras, Forcas. Also known as Furcas. Furcas is also found in the Lemegeton and Johann Wier’s Pseudomanarchia Daemonum.
He is known to teach logics and the secrets of plants and gems, gives invisibility and reveal hidden treasures.
What is most interesting about Furcas though is his rank. He is known as a Knight of Hell. A rank unique to him. Given the picture of him, and old knight on an old horse, I can't help but think of Don Quixote.
He is described in the Pseudomanarchia Daemonum as:
Furcas is a knight and commeth foorth in the similitude of a cruell man, with a long beard and a hoarie head, he sitteth on a pale horsse, carrieng in his hand a sharpe weapon, he perfectlie teacheth practike philosophie, rhetorike, logike, astronomie, chiromancie, pyromancie, and their parts: there obeie him twentie legions.So despite what sounds like a lower rank he still commands 20 legions of lesser demons. Given his name the "sharp weapon" is assumed to be a fork of some sort. The AD&D 1st Ed Monster Manual 2 attaches him to Dispater, the oldest of the Arch Dukes. It could be that Furcas was a knight in whatever service he was in before his fall and he still considers himself such. This might given him some sort of twisted sense of honor; somewhat like the character Orcini from Doctor Who. I think it would be interesting to know more about his background. Maybe he was once and noble and honorable knight till following his Master to Hell. Maybe he is just as evil all the same.