It was a consideration I've had for quite a while, and I'm going to see what ideas others might provide. What I have is a tiefling Bard, of the Negotiator archetype, who focuses strongly on the lawful and orderly side of Asmodeus with consideration as well on strictly inforced contracts. The party face, in making agreements through Diplomacy, Intimidation, and Bluff with perhaps a properly cast spell to help in overcoming a challange, broker deals, and even gain allies.
One who very much plays off the idea that, if a person doesn't take the time to read the fine print, it's their own fault if a deal doesn't go the way they expected. That it is more the written oath whuch is stronger simply a spoken one. To definitely get an agreememt in writing whenever possible, and to know what you're getting unto. Otherwise, another may very well exploit loopholes written into the agreememt or contract.
What's great about the Negotiator archetype is in how it actually had a class ability called Binding Contract, that allows a character to make a contract that is bound by geas effect. Which is phenomenal for such a concept and character idea. Finally, with a very classic devilish look in red skin, horns, cloven hooves, and pointed prehensile tail. Why? Well, because I think it would be more fun that way. Chuckles
Class: Negotiator (Bard)
Alignmemt: Lawful Neutral
Alt. Racial Traits: Feindish Spinter, Prehensile Tail.
Feats: Skill Focus (Diplomacy), followed by Diabolical Negotiator.