Nadaz was a purple-robed rat in the kingdom of Malkariss, and leader of the Blackrobe Rats. He acted as a sort of mouthpiece or viceroy for Malkariss, conveying recent happenings and receiving orders from the polecat. He was in charge of the slaves and led the army when Matthias attacked, though he didn't actually fight. His title was "Voice of the Host."
When Nadaz realized that Malkariss would lose to Matthias, he hid himself in the vacant polecat statue and began to dream of being the new ruler after his demise. He was killed when Matthias and Orlando the Axe hacked down the statue, causing the underground world to collapse in the process.
Nadaz was known to wield a spear with a skull on top of it, and used this to command his ruthlessly efficient but completely silent Blackrobes.
Nadaz from the French cover of Mattimeo
Nadaz from the Redwall TV Series