Threetooth was a rat in the gang of Groffgut, aptly named because he only had three fangs. He was the most rebellious of the gang and disagreed with the attempt to take Redwall Abbey. He was whacked in the head by Abbess Lycian with a teapot in an attempt to climb over Redwall Abbey's walls; this caused him to lose the rest of his teeth.
After Groffgut was slain by Banjon Wildlough for killing Brinty, and Frogeye and Plugtail were devoured by a gannet that was forced out of the Abbey gates, Threetooth fled into Mossflower Woods and was never mentioned again.