Marlfox

A villainous new presence is aprowl in Mossflower Woods--the Marlfoxes. Stealthy, mysterious, they can disappear at any time, in any place, and they are out to plunder and destroy everything in their path. And when they reach Redwall Abbey? They ruthlessly steal the most precious treasure of all--the tapestry of Martin the Warrior. It takes Dann Reguba and Song Swifteye, children of warrior squirrels, to follow in their fathers' heroic footsteps, and together with the young shrew Dippler, and Burble the brave water vole, they embark upon the seemingly impossible quest to recover the famous tapestry--to the ominous island domain of the Marifox clan and its evil leader ...

This is #11 in A Tale Of Redwall.