Sister May was featured predominantly in Mattimeo, however, she may also have been present at the time that Redwall took place. She was the Infirmary Keeper and one of the three who healed the bird, Stryk Redkite. Stryk Redkite shows her appreciation for Sister May by saving her from attack and naming her offspring after Sister May: May. She was known for being very clever. Sister May is also known for having made a sleeping potion that was used to capture three magpies who were stealing from the orchard. Other notable acts were her biting the raven leader, Ironbeak, and catching a grayling when Matthias was too weary.