Our tradition of Halloween was passed down from one of the ancient Celtic Fire Festivals, Samhain, (pronounced sow’ in). Each of the 4 fire festivals were celebrated at the midpoint between the 4 equinoxes, representing the Celtic view of the balancing of light and dark forces.
Samhain marked the end of the harvest, the end of the “lighter half” of the year and beginning of the “darker half”. It was traditionally celebrated over the course of several days. Many scholars believe that it was the beginning of the Celtic year. It has some elements of a festival of the dead. The Gaels believed that the border between this world and the otherworld became thin on Samhain; because some animals and plants were dying, it thus allowed the dead to reach back through the veil that separated them from the living. Bonfires played a large part in the festivities. People and their livestock would often walk between two bonfires as a cleansing ritual, and the bones of slaughtered livestock were cast into its flames.
The Gaelic custom of wearing costumes and masks, was an attempt to copy the spirits or placate them. In Scotland the dead were impersonated by young men with masked, veiled or blackened faces, dressed in white. Samhnag — turnips which were hollowed-out and carved with faces to make lanterns — were also used to ward off harmful spirits.
So now that we have an overview of ghosts and jack’o’laterns we turn to another symbol of Halloween, the witch. In Irish mythology this image is represented in the more complex form of the Morrigan, a diety of three persons (said to be sisters) which represent the dark forces of the Moon. It was not unusual in pre-Christian religions to represent a powerful female deity in three aspects since this followed the natural cycle of the Moon, with the New, Full and Balsamic moons representing the life cycle of women, maiden, mother and grandmother.
The Morrigan, was the dark goddess of war and prophecy, and also said to protect the sovereignty of kings (i.e. nations). How she is related to Halloween is in the story of the fight over Ireland between the enemy Fomorians and the people of the Sun God, Dadga, the Tuatha Dé Danann. To insure victory in battle, Dadga performs with the Goddess of War, the Morrigan, the sacred ritual hieros gamos on Samhain itself. Thus ritual magic performed under the aegis of women of power was forever wedded with the day when the veil between this world and the otherworld was thin enough for ghosts to visit the living.