SOW-in
The festival marking the start of the dark half of the year, when the boundary between this world and the Otherworld was said to grow thin.
Samhain fell around the first of November, at the midpoint between the autumn equinox and the winter solstice, and marked the end of the harvest and the beginning of the Gaelic year's dark half. Cattle were brought in from summer pasture, stores were counted, and communities gathered around bonfires whose flames were carried home to relight household hearths for the winter ahead.
Irish tradition holds that on Samhain the boundary between the human world and the Otherworld grew thin, letting the Aos Sí — the people of the mounds — move freely, and the dead were thought to walk among the living. Several of the great Mythological Cycle tales are set on this night: it is at Samhain, by the river Unius, that the Dagda couples with the Morrígan in Cath Maige Tuired, securing her aid against the Fomorians before the Second Battle of Moytura.
The festival's customs of divination, disguise, and appeasing wandering spirits passed down through the centuries and, carried abroad by Irish emigrants, gave rise to the modern Halloween.