Scragg was a weasel who was enlisted into the horde of Cluny the Scourge. Smarter than the average horde-beast, Scragg would have made a valuable captain. Cluny knew this and was considering promoting him. This made Cheesethief jealous, and the rat pushed Scragg out of the tall elm during the plan to use a plank to scale the walls of Redwall Abbey. When that failed to kill him, however, Cheesethief returned to the site of the fall and killed Scragg by choking him.
In the Redwall TV Series, Scragg is a rat, but this is a mistake, because when listing the dead Cluny calls out "Scragg the weasel."