Sister Sloey was a young female mouse of Redwall Abbey. As a Dibbun she was friends with Gubbio. During a game of hide and seek, Sloey fell down a former tower of Kotir that was causing one of the Abbey walls to sink. Skipper dove in after her and rescued her, saving her from a giant yellow eel.
As an adult, Sister Sloey became the keeper of Redwall's Infirmary. She was fairly quiet, and described as a sedate old mouse, but was not without a sense of humor. She and the other infirmary helpers helped to treat Florian Dugglewoof Wilffachop's "war wound", which turned out to be nothing more than splinters from sitting on a wooden salad fork, much to their annoyance. Later, she was struck with a fit of hysterical laughter when she overheard someone referring to him as "Florian Forkbottom".