Adder Stones (sometimes
also called hag stones, witch stones, serpent’s eggs, snake’s eggs, Glain
Neidr, Milpreve, adderstanes, Gloine nan Druid, aggry, or aggri) are stones,
usually smooth or glassy, with a naturally occurring hole bored straight through
it, typically from water erosion or natural damage.
That said, there are no shortage of stories claiming these
stones have a more unnatural origin. One claims that they are formed from the
hardened saliva of a great number of serpents, massed together, and the holes
are from their tongues. Another claims the stones are actually the heads of
Adder stones feature prominently in Welsh mythology and
Druidic culture. They were believed to have magical powers and thought to
protect people from a gamut of problems, ranging from eye diseases, evil
charms, nightmares, whooping cough, and snake bites. It was also believed that
if you looked through the hole in an adder stone, you could see through the
disguise of a fairy or witch.