Many devils are about contracts. The phistophilus, or contract devil, is really about contracts. The scribes, librarians, and record-keepers of Hell, these devils are in fact literally draped in documents, and they use these scrolls as whips in a way that a human librarian could only dream of. (That’s not even including their gore or impale attacks.)
With their ability to offer three wishes or the services of another devil, in the mortal world they are truly iconic examples of the bargaining power of Hell, the crimson dealmakers who seems to arrive at the most opportune moments to strike a bargain. When encountered in Hell itself, on the other hand, they are the symbols of a bureaucratic, legal, and recordkeeping system more byzantine and convoluted—yet utterly ordered—than anything else in existence.
A contract devil serves an infernal duke of broken vows and undeath. Mortals who sign his contracts do not immediately forfeit their souls upon death, but instead reanimate as jiang-shi vampires, each with a copy of the implicating document nailed to its head. The contract devil is always accompanied by at least two of these hopping vampires at all times.
A good-natured rogue used the last wish in his luck blade to restore a friend to life—never realizing the sorcerer had once signed away his soul to a contract devil. Now the sorcerer has vanished and the rogue is on the run from bearded devils sent by the phistophilus to punish his interference. The attacks will not stop until the contract devil is defeated or the rogue serves up a suitable soul to make up for the truant sorcerer.
A party’s barrister is defending their claim to a magical artifact when he is stolen away by a plane-shifting contract devil. “He’s been subpoenaed as an expert witness,” is all the devil says before sweeping the man away. With the artifact impounded and their case in jeopardy, the party has little choice but to go to Hell and rescue him, arriving in the granite city of Archvilius. Researching the right precedent to guarantee their friend’s release in Archvilius’s many libraries is possible, but would take months. With the aid of the right tiefling law clerk, however, they will learn that the contract devil has rivals who wish to see him humbled—so much so that they might even forgo the usual price of a soul for their aid.
—Pathfinder #12 86–87 & Pathfinder Bestiary 3 76–77