A hag with sharp green teeth and long green hair that is said to inhabit the river Tees. She waits in the water for the approach of unwary humans, especially naughty children, and she grabs the ankles of those who unknowingly wander too close to the water's edge. Some acconts show her dragging her victim to an underwater lair, where she devours them. Others simply show her pulling her victims underwater to drown them. Obviously, swimming or wading in this river is strongly discouraged.
Warnings that Peg Powler may be nearby include the presence of green foam or froth on the river (known as Peg Powler's Suds) and/or the presence of green surface scum (known as Peg Powler's Cream) on slower sections of the river. The alder tree was considered as a charm that held evil faeries at bay, as in this Mother Goose ryme which shows a fear of water faeries like Peg Powler:
"Mother, may I go out to swim?"
"Yes, my darling daughter.
Hang your clothes on an alder limb
And don't go near the water."
Bean-Fionn is a general name for all types of drowning faeries. Peg Powler is also known as Jenny Greenteeth, a similar green hag who is known to haunt stagnant pools of water in Lancashire. Another green hag, Nellie Longarms, is thought to inhabit Derbyshire, Cheshire, Lancashire, Stropshire and Yorkshire. Interestingly, a German version of the Bean-Fionn, called the Weisse Frau, was said to love children and protect them. She was also said to help travelers, but she angered easily, especially if you were to abuse a child.
The tales were no doubt created to scare young children away from the precarious banks of rivers and streams. Some variations of the story even make sure to specify that the children who were attacked were explicitly disobeying their parents' wishes.