Vain and bad-tempered, Illyere lived alone in the collapsing Althier, along with her two consorts, Myrrh and Lutur, though none were allowed to enter her chambers. She gave orders through a crack between the door and the floor; most of her horde had never seen her in person. She claimed to be a soothsayer, one who communicates with the dead and interprets their messages, and she relied heavily on this to hold her position as leader of the Firebearers.
She would constantly invent new prophecies in which she would be guaranteed another full year of power by the approval of her ancestors (Vilaya implied to be among them). Illyere carried a thin, polished hardwood stick, her only weapon. It is unsure whether she had ever learned to use it.
During a dream, her mother Rengia visited her and instructed her to attack Redwall Abbey and take it as her own, to establish a kingdom in which the Firebearers would rule for eternity. Convinced that she had had a true prophectic vision, Illyere began mounting raids on the abbey, stealing their Dibbuns and ransoming them in return for control of Redwall. Once this failed, she moved towards a more strategic move, successfully burning the main Wallgate down and trying to enter the abbey by force. During the battle, she sent her commanders Dayrose and Fieldrush into the flatlands in search of the legendary Grulluba Axepaw .
Illyere was killed by Lutur after instructing the ermine to kill her own sister and her commanding officer, Zephyranth .