The Liberators of the Coin is primarily an organization Halflings devoted to (insert trickster/thieving/Halfling god). They pattern themselves after a myth of the god stealing gold coins from his brother on the evening of his wedding. The stolen gold was a part of the wedding ceremony and its absence meant that the ceremony could not proceed. The theft resulted in the trickster being able to marry his brother’s intended.
The party is walking through the forest at night when they come upon a clearing. Half a dozen black-robed corpses lie scattered across the ground, and a pentagram of blood is shoddily drawn in the dirt.
It seems these people summoned something they could not control. Whether or not the demon returns is up to the GM, but it would be just as rich if the demon never returned, and for the rest of the night, every stray sound or odd shadow will be jumped at!