Hag stones, also called holey stones, holed stone, fairy stones, Odin stones, spindle whorl or adder stones are stones with a naturally occurring hole through them. These are often found in or near water. Hag stones have many magical powers attributed to them, including protection, healing, and the ability to see the fae.
The term hag stone alludes to the belief that these stones are capable of breaking hexes. According to British lore, the adder stone is traditionally created either by a group of snakes blowing a bubble and rolling it around until it forms a crystalline structure((https://www.sacred-texts.com/neu/celt/lrb/lrb12.htm)), or the snakes drip venom on the stones to create a hole, which they pass through to assist in the shedding of their skin(https://www.sacred-texts.com/neu/celt/rac/rac24.htm).
The name Fairy Stone comes from the tradition that the fae are visible viewed through the hole in the stone and that it offers some protection from and even control over faery creatures.
The term Odin stone is about The Stone of Odin, a large, holed standing stone that stood on the Standing Stones of Stenness in the Orkney Island. The stone was about 8 feet tall and had a hole about five feet up that was large enough for people to put their hands through, which it, it is said, they would do to swear oaths, including those or marriage.
This stone was destroyed by the landowner Captain W. Mackay in 1814 because he was annoyed by frequent visitors to the stone((https://canmore.org.uk/site/2128/stone-of-odin#:~:text=The%20Stone%20of%20Odin.%20This%20stone%20formerly%20stood,hole%20at%20about%205%20ft.%20from%20the%20ground)).
As a side, there is also a Welsh tradition of the Stone of Garonwy, (Lech Ronw or the Slate of Gronw) a standing stone with a hole through it near the river Cynvael, in Ardudwy. This stone, it is said, was placed there by Garonwy Pebyr, in hopes that it would absorb the spear strike of Llew Llaw Gyffes, but the spear passed right through the stone and killed him anyway((https://en.wikipedia.org/wiki/Llech_Ronw)).
Large stones with natural holes in them, those that are large enough to put a limb through or your whole body may be used to mark periods of transition. If two people clasp their hands through such a stone, the vows they give each other are unbreakable. Passing the entire body through the stone is an effective feature of any rite of passage conferring protection and strength as one moves forward into the new phase.
Magical Attributes of Hagstones
Hagstones can be used as protective wards. They can be strung on a cord and hung on any object to protect it, at any thresh hold to protect the building or land or worn on any person to protect them. They are considered especially protective against harmful magicks and spirit beings. These were particularly popular for protecting ships, livestock, and children.
A hag stone hung on the bedpost is said to improve a couple’s chance of conceiving.
One can see the unseen, including the fae, peering through a hag stone.
Hagstones are generally formed in water and resonate with the energy of the element of water.
Obtaining a Hagstone
By most accounts, one should obtain their own hagstone rather than purchasing one or receiving one as a gift. Hag stones are most often found near or in water, especially moving water or the ocean.
Learn More Online
What is a Hagstone and Why Are They So Special? at Mystical Raven
Crystal of the Week: Hag Stones at Speaking of Witch; Wands & Magical Things