Now, a name like "Gambit Demon" doesn't exactly inspire suspicion, and neither does the thought of striking mysterious "deals" with them. However, there is no need to worry, as I have devised two strategies to ensure that the Gambit Demon is incentivized to side with town and to obediently hand out roleblocker shots to whoever we agree should get it.
Strategy One: The Leash
Because my plan involves no player taking a power beyond tier 1, the Gambit Demon will have to give seven different players a tier 1 power in order to win. This means that we are essentially putting a leash on them, forcing them to work with us and give players we select a tier 1 power over the course of 7 days. By controlling the circumstances in which the Gambit Demon is permitted to win, and ensuring that they won't actually achieve their win condition until later in the game, we force them to side with us early in the game in order to reach that win condition. This protects against scumsiding, and also against situations where the Gambit Demon achieves their win condition and is free to rampage around the thread causing chaos as they please.
Strategy Two: The Dead Man's Switch
One of my major concerns when constructing this strategy was the possibility of the bargain being more Faustian than expected - perhaps taking a power would have some negative side effect inflicted on me that the Demon has chosen not to disclose. Or perhaps the Demon would get some measure of power over me as a player if I take their bargain. Or perhaps they're simply lying about some aspects of their role claim (remember, I have reason to believe that their win condition is accurate, but not that their role claim is) and can't be trusted.
For this reason, I have established a Dead Man's Switch strategy that allows the Gambit Demon's role to be kept secret (to protect them from being killed by the Obliterator) if they cooperate, but leaked to the rest of the thread if and only if something goes wrong. They are incentivized to make sure this does not happen, because if their identity is leaked, they will be killed either by the Obliterator or by townies, and therefore be unable to achieve their win condition (which is why the Leash is important for keeping them in line, by allowing us to hold this Damocles' Doom over their head).
The strategy is as follows. When the Gambit Demon contacts a player to offer a bargain to them, they gain BTSC with that player. (Remember, this is a player that's been agreed on to be unimpeachably town by the rest of the thread.) As stated in the plan, they will accept the deal and again the tier 1 roleblocking power. They will also, at the same time, establish the Gambit Demon's identity. This can be done in a multitude of ways, or as the player sees fit. If you don't have a better way, the Gambit Demon will tell you what method I used to establish their identity and then have you use it to prove their identity to you.
Under ordinary circumstances, the Gambit Demon's identity is to be kept secret to protect against Obliterator. But if anything goes wrong, the players who know the Gambit Demon's identity will reveal it to the thread, and the town will then execute them, preventing them from completing their win condition. The threat of this will keep the Gambit Demon in line. Things going wrong include: the Gambit Demon not offering a bargain to the person we agreed on, an undeclared negative side effect happening on people who took deals, the people who took deals previously dropping dead without a good explanation for why, or any other evidence of foul play or treachery.
If we have falsely cleared a wolf, and wrongly selected scum to receive the Gambit Demon's bargain, then scum will be privy to the knowledge of who the Gambit Demon is. If the Gambit Demon themselves dies under suspicious circumstances (eg. the Obliterator's soup kill), then we will know that one of the people who we trusted enough to give a roleblock to was a deepwolf in disguise. This is still a positive development for us, because it proves the existence of a deepwolf while we have already gotten to reap some benefits from the Gambit Demon (in the form of giving townies free roleblocks). If the mafia want to waste their nightkill on a 3P slot and work to pass it off as something other than a Gambit Demon snipe (which would out the existence of a deepwolf), that is also fine by me.