Desmaer was a tiefling I used one of my campaigns awhile ago. I lost his sheet so I am kinda just doing this from memory. If I had been able to I would have used flyingpoo22's Tiefling idea.

Desmaer if a bald human looking Tiefling except for that he has a blue devils tail and Black eyes. Desmaer wears dark blue-black business clothes, a bowler cap and round mirrored glasses, despite the medival time frame.
Desmaer is a mid high level rogue and prefers to make others fight his battles for him, often summoning devils through scrolls and magic items. When forced to fight Desmaer will attept to buy his life before attacking, if he succeeds in buying his life he will then attack in order to reclaim lost gold.

Desmaers job is the most interesting part of him though. When somebody says they would make a deal with the devil Desmaer acts as an intermediary. Desmaer can sell any item to a person in return for 3/4 of its normal price as well as their soul. As soon as somebody sign one of Desmaers contracts their soul belongs to the devil that crafted the item. All items are as asked for, no cursed items or tricks are within his contracts. He never tells the people he deals with all the details apart from the good price. Desmaer prefers to deal with fledgling adventurers and the rich while they are drunk and easy to manipulate. As soon as somebody who has made a deal with Desmaer dies their soul goes to the devil who made the deal, to be dealt with at the devils pleasure. Those that die cannot be raised by any spell due to the binding of the contract and the item they aquired goes back to the devil.

When Desmaer was young he made a deal with the devil lords, writing the contract himself. If Desmaer was able to meet a certain quota of souls he was to be turned into a true devil when he died. He could become better types of devils the higher above his quota he got if at all. Nobody but Desmaer and the devil lords know what these numbers are or how many he has already filled.

Desmaer carries very little on him, prefering to not seem a good target for thugs. But does carry many hidden magic items and bags of holding with magic scrolls. His most treasured possesion is a briefcase that holds all of his contracts. Any contract he wants is immediatly on the top of the briefcase as well as his special contract signing pen.

Anything to say? I didn't go into great deal about his stats because it was awhile since I made them and as I said I lost his sheet. All I can remeber if high skills in bluff and forgery.

He was an effective enemy in my campaign until the mage blew him up and sent his corpse into another dimension. He returned later as a Pit Fiend and almost destroyed them.