The Broken Promise was a merchant ship that had been used for many years to ship potions made by the apothecaries of Mag Mel to clients from all over the Myr who sought their cures.  It was a highly secretive practice during Chamberlain Llyr's prohibition of potion-making but it was also highly lucrative.  When the prohibition was ended, the captain and crew of the ship had to content themselves with the transportation of stolen goods which was a far less profitable business arrangement.