Nagru was a large grey fox who ruled the Land of Ice and Snow in the far north. He claimed to have killed a wolf named Urgan and took his skin as a trophy for himself, wearing both the skin and skull of Urgan and calling himself the Foxwolf. It was revealed by his mate, Silvamord, that Nagru had not actually killed the wolf, but had found him dead in a blizzard and took his pelt. Foxwolf also took the wolf's name, Urgan, and then reversed it: Urgan Nagru. He named himself this so that his enemies would known that he could come at them from every direction. His original name is not known. His weapons were hooked iron claws that he attached to the paws of the skin. He also wielded a sword.
The Foxwolf eventually grew tired of the cold northlands; he took Silvamord and his army of grey rats across the sea to Southsward, a land ruled by Gael Squirrelking. Feigning to be weary travelers seeking refuge, Nagru and Silvamord infiltrated the kind king's castle and took it over, keeping the king and his family captive. He ruled the castle for a few years without much resistance, until some wandering mice warriors from Redwall Abbey arrived and helped to gather and army against Foxwolf. In the final battle, Urgan Nagru fought the sea otter captain Finnbarr Galedeep. The Foxwolf nearly killed the otter, but Finnbarr eventually grabbed him bodily and smashed Nagru's head into a thick tree, driving the wolf skull fangs into his brain and killing him.
Even though Nagru and Silvamord were mates, they distrusted each other and constantly bickered, even to the point of violence.