The dusters have a saying: "Blood or coin, the Carta always gets its cut." When Beraht was running Dust Town, he took the saying literally. He commissioned a pair of wicked blades made by SmithHouse Dural. Beraht gave one to his right hand, Jarvia, and the other to his second, Karshol, so that whatever hand of the Carta you got, it'd be holding a big sodding knife. Beraht wasn't exactly a poet.
Jarvia was killed in Dust Town during the messy succession, and Karshol turned all of Orzammar upside-down looking for her blade. Some duster struck gold finding that blade and must have been clever enough to sell it right away. Stone only knows what Karshol will do to the luckless clod who has it when he finds it.