Thrugg was an otter from Redwall and the brother of Thrugann. When the Abbey was stricken by the deadly Dryditch Fever, he set out with the Dibbun dormouse Dumble to find the cure - the Flowers of Icetor. On his journey, he defeated a roving band of foxes who tried to rob him and Dumble and a large group of crows whose territory the pair passed through (with the help of Laird Mactalon's clan). Thrugg was a fearless warrior who was willing to go to any lengths to save his beloved abbey from sickness. He demonstrated this when he stood up to the Wild King MacPhearsome so he could get the Flowers of Icetor growing near his nest.
He later returned to Redwall with these flowers and also brought along his and Dumble's newfound friends, the clan of falcons and Wild King MacPhearsome. Tudd Spinney presented Thrugg with a specially carved spoon and bowl made of apple wood with his name on it, which Friar Bellows promised would be filled with Hotroot Soup any time he wanted as a gift for saving the abbey.
Thrugg was the last otter character to use nautical terms in everyday speech (the species' defining characteristic in the previous three books).
Thrugg was known to be a fierce fighter and warrior, and demonstrated this when facing a large group of crows. When Dumble was injured, Thrugg went into what may be considered a state of Bloodwrath and drove off the crows, albeit temporarily.