The Gonfelin Thieves were a tribe of mice descended from Gonff the Mousethief. They were kicked out of Redwall Abbey after stealing a priceless ruby. They moved into the surrounding forest, keeping the ruby they had stolen as a family heirloom to be passed down from generation to generation. For hundreds of seasons, they remained secreted in the woods against the knowledge of the Redwallers, until Bisky happened to trespass on their territory. They agreed to ally themselves with the Redwallers and Guosim against the Painted Ones, and later against the Doomwytes of Korvus Skurr. Once these enemies were defeated, they moved into Redwall Abbey once more, where it was suggested they lived from then on.
The name of a member of the Gonfelin tribe always ended with the letter O, and they addressed other creatures as if their names ended with O as well. For example, Abbot Glisam was referred to as "Abbo". They were very argumentative and occasionally violent, with sandbags as the weapon of choice for settling private disputes. However, for serious emergencies, they possessed proper weapons, such as knives, battleaxes, and nooses for strangling.
The Gonfelin Thieves appear in Doomwyte.