The Little Sisters are a vampire cadre who operated a field infirmary outside the town of Eluria.
Presenting themselves as a quasi-monastic order similar in fashion to nuns, they prey on the sick and injured by first nursing them toward health (through an as-yet unknown association with the Cam Tam), and then feeding on them.
The Little Sisters can appear either in human form or in their native (and monstrous) vampiric state at will.
In the Dark Tower Series[]
In The Little Sisters of Eluria, they succeed in capturing Roland Deschain, who later escapes with the help of Sister Jenna.