the Bean-nighe is a type of banshee from Scottish folklore that would take the form of an ugly old woman who sat by rivers or streams washing clothes, they were said to predict death and misfortune, often mourning over the clothes of those destined to die.
Despite their frightening appearance the Bean-nighe were completely neutral entities and could grant wishes or bestow knowledge upon those who approached them respectfully, they could also be forced to grant similar boons if someone sneaked up on them and restrained them but forcing such things from the Bean-nighe could carry significant danger as she could cause people who displeased her to lose the ability to use their limbs, effectively paralysing them.