Need suggestions, player wants to make a deal Options

[Moon-Hawk]

I need to tap the collective Dumpshock consciousness for ideas.
A player wants something, and is willing to make a deal for it, but I'm not sure what to give or take.

The situation: The PCs are in a gang-type setting. They all belong to one gang, and there's a big rival gang trying to kill them. After much aggression over many sessions, things are really coming to a head and the enemy gang is going to attack their turf in an all-out assault with superior numbers and the PCs are going to have to defend themselves. One PC in particular is a mage who's character has always been very protective of the other members. His player wants to know if there's anything he can do to gain an edge for the team in the coming fight. The player has told me that the character would pretty much be willing to sell his soul to guarantee a victory.

Now I'm willing to make deals with players. ex: Cut the programming time in half in return for an addiction to Long Haul, etc.

So what could I give him? High force spirit? What kind of an edge (unconventional ideas welcome!) could he gain?
And what do I take in return? Geas? Loss of magic? Magic flaws? (again, unconventional ideas are fine here too)

Help me out, please. Get creative; get mean. :-)