Sister Fumbril was a big, jolly female otter Infirmary Keeper and Herbalist of Redwall Abbey during the time of Vilaya the Sable Quean. She was a favorite of the Dibbuns, who called her "Sis Fum", for her jocularity and fun songs which she played on her fiddle. She was good friends with Abbess Marjoram.
Sister Fumbril played her fiddle in the Bard O' Redwall contest, singing an upbeat dancing song, which was so popular with the Dibbuns that she sang the song three times. Fumbril took care of Clarinna when she journeyed to Redwall after her babes were stolen by the Ravagers. Also, she tended her wounded during Zwilt the Shade's attack on the Abbey. She was a minor character, not much else is known.