Here is a teaching I have done in the past on Halloween.   Unfortunately, I did not reference where I got all this information, so any plagiarism is unattended.   The outline at the end is original:

Halloween’s unsavory beginnings preceded Christ’s birth when the druids, in what is now Britain and France, observed the end of summer with sacrifices to the gods.  The holiday is rooted in the Celtic festival of Samhain (pronounced sow-in), which came at summer’s end.

Celts believed that on the night before the New Year (which began on November 1st), the boundary between the worlds of the living and the dead became blurred.

Samhain beckoned to winter and the dark nights ahead . . . pointing to winter as a season of death.  They believed Samhain, the lord of death, sent evil spirits abroad to attack humans, who could escape only by assuming disguises and…