Hag stones or Donuts are stones that have a small hole running all the way through them. They are usually found in streams or rivers and at the seashore, where the action of running water has created the hole in the stone. It is common belief that magic cannot work on running water, and as the stones are tunnelled by the force of this element they retain its beneficial influence.
This makes them very good charms for deflecting away negative energies from the bearer. Hag stones are also known as Ephialtes stones, Holy stones, Holey stones, Wish stones, even Donuts. Nightmare stones and Witch Riding stones. In medieval times, they were credited with the power of protecting both people and animals from the influences of evil spirits and were hung around the neck or on the key or door to cattle stalls and stables.
The most interesting quality that Hag stones possess is the perceived ability to enable the bearer to see fairies and be protected from their enchantments. Such a charm would have been especially useful at Samhain, when the veil between this world and the fairy world thins.