Pieces of the Puzzle
Gaston Red is a traveler passing through Averlain, identified to you by the demon Lily. He has fiery red hair and a scar running down the right side of his face; he is neither tall nor short, but has a very athletic build. He is adorned in fine clothing and armor, and carries a rapier with him.
Gaston is almost certainly an adherent to the Darkness, given his consorting with Lily and possibly other demons. He has work to do in the region, he says, some of which was in Brush, and has not offered any assistance of labor to the party so far. However, he did point you to the priest, Jespen Gifter, so that you might take out bounties for the cleric.
It could be a trial, perhaps that Gaston is wanting to test your mettle before pointing you in a new direction.