Humbert Tarn revealed that the assassin's true name is Corborin, and that he plans to leave Erenen by way of ship to Aregrionno from Eastport by the end of the week.
Get your pound of flesh after the attack on Nova Amaril and kill Corborin before he's out of your reach.
On the 28th of Summersdawn, the Raven Shield sprang their trap, but Corborin managed to flee.