"Samhain marked the end of the harvest, the end of the "lighter half" of the year and beginning of the "darker half". 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. 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"
Samhain was also the second band of Glenn Danzig, and I really like this song. Let the day begin.