@Partisan: Sometimes, I imagine Warren's former colleagues (the Blackblades) wanted to assassinate Gregar when he ascended to the throne. This divided the Blackblades; Warren and his compatriots wanted to trot into the Hoffburgt and slay the Bastard then and there, but the others advised against it, so the Blackblades disbanded. Warren and his mates never got the chance to kill Gregar.
Also, Warren hates the Sawarim so much, while in Redsand he was actively trying to get the Sawarim to attack Broacien so as to start a war, and promptly destroy the ibn Wahad sultanate altogether. He murdered every Sawarim he came across - be it man, woman, or child, trying his best to get them to invade Redsand.