Dingeye was a stoat soldier in Ferahgo the Assassin's horde.
He and his "mucker" Thura deserted the horde and wandered about aimlessly until they eventually ended up at Redwall Abbey. There, they were treated as guests, although they repaid the woodlanders by accidentally shooting Brother Hal in the neck with a bow and arrow. Afraid they would suffer dire consequences, the two stoats stole Martin the Warrior's sword and fled into Mossflower Woods.
When Thura soon died of the dreaded Dryditch Fever in the depths of Mossflower, Dingeye continued without him, only to be caught up with by Ferahgo's tracker Dethbrush, who beheaded him.
It should be noted that although he and Thura never did anything truly good, they were much kinder and friendlier than most vermin, and they were never known to kill intentionally. Also, they were only soldiers of Ferahgo because of their desperation.