Cailleach is one of the more ancient Celtic goddesses whose lore and worship still survive in many European countries today. She is the very ancient Hag-aspect of the Triple Goddess, who was known by many names throughout the Celtic countries (e.g., Ireland and Scotland), such as Cailleach Beara, Cailleach Bheur, and the Crone of Beare. In some parts of Ancient Britain, this deity was the Goddess of Winter, who was reborn every Samhain. Her time begins on Samhain, when she leaves the mountains and begins her walk across the lands bringing the winter storms, snow, and death. Thus Cailleach has the power over the weather and storms of winter. She is also called “the daughter of Grianan,” the winter sun. On the old Celtic calendar, there were two suns, 'the big sun,” which shines from Beltane to Samhain, and 'the little sun,” which shines from Samhain to Beltane Eve.

According to legend, the Cailleach can transform herself from a terrifying hag in the winter half of the year and into to a beautiful young maiden in the summer half. As “daughter of the little sun,” the Cailleach is an elemental power of winter, the cold, wind, and tempests. She comes into power as the days shorten and the sun courses low in the skies. She carries a slachdan (wand of power) with which she shapes the land and controls the weather. (The Cailleach's slachdan relates to staffs used by Celtic shamans.) While the Cailleach's slachdan resembles the Fé and magic wands of the Celts and Norse, it also holds cosmological significance as the power of cold, darkness and winter. It symbolizes the active force of the Old Goddess in Celtic culture. When she hurls it she creates rocks in Ireland and rearranges the coast of Scotland. When the light half of the year begins, she hurls her slachdan to the base of the (evergreen) holly or gorse, storing her power of the cold and dark there until the advent of winter. The last spurt of harsh winter weather is called A' Chailleach. People observed and watched for definite meteorological changes that signaled the coming of the Cailleach, who brought snowfall over the heather-dyed hills and fields. Various accounts show Cailleach Beura and her helpers riding on wolves and wild pigs (like Norse and Russian witches) especially in February storms. Scots call her the “Old Wife of Thunder.”

The great Old Goddess of Ireland was the Cailleach Bhéara, or Hag of Béare in Munster. She “existed from the long eternity of the world.” Her great age was a sign of power, truly venerable, and proverbial: “as old as the Cailleach Bhéarra.” The Cailleach has universal qualities; she is not a goddess of fertility or death or any one thing, but a deity who is both transcendent and immanent. She is connected with rivers, lakes, wells, marshes, the sea and storms; with rocks, mountains, boulders, megalithic temples and standing stones; and with cattle, swine, goats, sheep, wolves, bird, fish, trees, and plants. Countless Irish myths tell how the Cailleach constructed huge mounds, megaliths, and towers in a single night.

The Cailleach is one of the dark goddesses, her color being blue-black. It is thought that the blue-black color association is due to Cailleach’s time beginning at Samhain, in that she brings forth the bitter cold of winter. In later times, the mythical witch-like figure of Black Annis is believed to have derived from The Cailleach. The Cailleach is a combination of the Underworld goddess and a faery. She has fangs and often sports three faces, making her a triple deity. Loosely translated into more modern Gaelic and then English, Cailleach means “old wife,” although some say that in the older Gaelic her name meant “one who is veiled”. This seems to refer to one of her aspects as a dark goddess—one who can see within the worlds of both the living and the dead.

Cailleach is of the “Ancients.” She is known as the “Crone of the Celts.” The figure of the Cailleach as the wise woman, the hag, or the Red Woman is part of an oral tradition that has its roots in pre-Christian Ireland. In the Irish Triads, the Cailleach is considered one of the three great ages: the age of the Yew Tree, the age of the Eagle, and the age of the Hag of Baere.

Knowledge of Cailleach's existence has been known since Neolithic times. Originating in Europe her worship spread with the Celts, who became the first inhabitants of the British Isles. Her many names spoken are as varied as her goddess aspects of war and love. Some of these were quite fearsome in nature (e.g., her aspect of war) and some not (e.g., her aspect of love). This shows the dual personality of this goddess, while some of the surviving legends also attribute a triple goddess aspect.

It is also said that within various incarnations some of the Cailleach’s other names were known as Blue Hag, Owl Goddess, Boar Goddess and Blue Crone Goddess. . Other depictions of Cailleach speak of her as an old hag with boar's tusks protruding from a blue mouth. Another casts her image as one-eyed and blue-faced, with the size of a giantess. Of the Celtic goddesses, Cailleach is thought of as the strongest of the goddesses. But Cailleach is not all destruction and fear. She is also worshiped as a protector and steward of wild animals, (in particular, reindeer and wolves). It is also said that She is the guardian of wells and streams, a fishing Goddess and hunting Goddess. There are other stories where she turns into a beautiful maiden.

In Scotland, The Cailleach was known as Scota and said to be the earliest known ancestor of the Scots. Initially, Scotland was called Caledonia or the Land Given By Cailleach. Scota was probably once a Mother Goddess in Egypt, but her myth and origins have become shadowy with the passage of time. In many tales, she was the mother of Amergin the Bard; in others, she was the mother of Goidel, who gave his name to the Gaels. She is said to have died fighting the Tuatha de Danaan in the Milesian invasion and thought to be buried near a dolmen in County Kerry, Ireland.

The Cailleach Bhearra, or the Hag of Beara, is also a wise woman figure embedded in the physical and mental landscape of western Ireland and Scotland.  Stories of her relationship with that rugged landscape and culture still abound. She had a love affair with a sea god and her petrified body overlooks the Ballycrovane Harbour, from which she is reborn at the beginning of each of her many lives.