Sister Viola was a prissy bankvole of Redwall Abbey. As a young creature, she was the rival of Tansy, of whom she was constantly jealous. Abbot Durral was kind to her and let her go out into Mossflower Woods under his guidance. However, Durral and Viola were captured by Lask Frildur and his lizards to be taken back to Ublaz Mad Eyes as prisoners for the ransom of the Tears of all Oceans.
Durral managed to help Viola escape, and Viola was led back to Redwall by two Guosim shrews, Jesat and Teno. However, she gave them the slip and stowed away on the Freebeast to come along with Martin II, Grath Longfletch and Clecky, Plogg, and Welko to rescue Durral.
As an adult, she became the Infirmary Sister of Redwall Abbey, and was known for her cure-all, seaweed and cockleshell potion. Just like her predecessor, Sister Cicely, she was a bit fussy and zealous, although she cared a lot about the safety and well-being of others creatures, young and old. She was one of the first to notice that Tansy and her friends were missing while searching the ruins of Kotir underneath Redwall Abbey.
Sister Viola also often acted as deputy Abbess when Tansy was busy or absent. She had a lot of authority and confidence but had trouble actually maintaining the order.
Not to be confused with Sister Violet.