The exact story of this Chosen of Mercury is left in the Violet Bier of Sorrows. However, it can be surmised that he was sent by the Bronze faction in yet another attempt to kill Twice-Blessed Raven.
The party discovered him chained up by an Abyssal and unconscious. He was slain in the chaos that followed.
He had a tricorn hat, an overcoat, and a starmetal-laced Firewand. The last appears to be some sort of artifact weapon, and the first has certain odd essence flows around it as well.
It's worth noting that at this point, the Bronze Faction has lost several members trying to kill Raven. As far as he can tell, it has adopted the tactic of using assassination attempts against him as a method of getting rid of "inconvenient" members, with the added bonus of a chance of enormous payoff if one were to succeed.