In order to spawn the Capuchehaies in the Ahgram Audience Chamber, you must Parley with the Advisors, Chancellors, and Petitioners that you find there. After a successful parley, they will run off, and another NPC will return in their place. There is a random chance that the returning NPC will be one of the Capuchehies who you can then Parley to get a writ. See Writs where the names of the Capuchehies are given and the Writs they start.