F is for Forcas

Appearing as an almost nude man with a long beard and white hair, Forcas is a knight and general in the service of the King of Hell. Despite his somewhat unruly appearance, he is a calm and serene warrior. He's also quite eloquent. He imparts knowledge of herbs, precious stones, logic, aesthetics, palm reading, pyromancy, and rhetoric. He is also able to impart the knowledge of turning one's self invisible. Finally, he has a magical ability to find lost things and treasure.

Forcas
Armor Class: 2 [17]
Hit Dice: 12
Attack: Spear (1d6, 40' range)
Special: See Below
Move: 12
HDE:  12, 2,000

Forcas and his mount, a stubborn immortal mule, are immune to nonmagical weapons. He can turn him and his mount invisible and unlimited number of times per day. If he throws his spear it will return to him the following round.

Summoning/Bargaining Ritual Modifiers: New knowledge (+2), rare herbs (+1 per 10 lbs)

Potential Boons: a palm reading, occultist becomes more articulate (+1 to Cha), occultist becomes more logical (+1 to Int), knowledge of gems, knowledge of herbs, knowledge of invisibility magic, knowledge of fire magic

Potential Banes: max HP lowered, character must bend will to superior logic, character cannot lie