Mangiz was a somewhat successful crow seer from the Northlands who served as General Ironbeak's strong right wing and consultant. He saw Redwall Abbey in his visions and advised Ironbeak to attack it, but when he arrived there, his visions were clouded by images of a mouse in armor, likely Martin the Warrior. Mangiz saw how much Martin meant to the Abbey residents, and advised Ironbeak to try and steal Martin's tapestry. The plan nearly worked but eventually failed.
Mangiz was very superstitious, but yet had a large influence over the beliefs of the rooks serving under Ironbeak. When Cornflower and Constance began playing their trick of dressing Cornflower up in Martin's old armor while Constance called out in a scary voice, Mangiz became afraid of Martin. The rooks also lost morale, often retreating to the dormitories and locking themselves inside. Mangiz wisely hid his fear, as General Ironbeak was not very tolerant with the rooks who were afraid. Mangiz also started lying about what he saw in his visions to please his General.
During the final struggle between the Redwallers and the birds, Ironbeak was killed by Stryk Redkite. Mangiz tried to rally the disheartened rooks, but did not see Constance coming and was slain by the angry badger mother.
Nelvana Redwall TV Series
In the Nelvana Redwall TV Series, Constance punches Mangiz, showcased by her punching the screen. His death mirrors that of Fangburn's in the previous season's finale, where a close-up of him screaming and a zoom-in of Constance's mouth appears, fading to black with a crunching sound in the background.