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 looking live evil spirits themselves.”

During the celebration, the Celts wore costumes, typically consisting of animal heads and skins, and attempted to tell each other’s fortunes.  By A.D. 43, Romans had conquered the majority of Celtic territory. In the course of the four hundred years that they ruled the Celtic lands, two festivals of Roman origin were combined with the traditional Celtic celebration of Samhain

In the seventh century, Pope Boniface IV designated November 1 All Saints’ Day, a time to honor saints and martyrs. It is widely believed today that the pope was attempting to replace the Celtic festival of the dead with a related, but church-sanctioned holiday. The celebration was also called All-hallows or All-hallowmas (from Middle English Alholowmesse meaning All Saints’ Day) and the night before it, the night of Samhain, began to be called All-hallows Eve and, eventually, Halloween.

The complications of Halloween go far beyond its pagan roots, however.  In modern culture, Halloween has become not only a commercial holiday, but a season of cultural fascination with evil and the demonic.  This fascination with the occult comes as America has been sliding into post-Christian secularism.

Halloween is a good time for Christians to remember  . . .

1.  The Devil and Evil spirits are real The Devil will seize every opportunity to trumpet his own celebrity.

2. Christians are not to communicate with the dead

We are not to attempt to communicate with the dead through mediums. ~ Deuteronomy 18:10-11
Lying spirits will attempt to deceive people. ~ I Timothy 4:1

3. Halloween is the same date as one of the greatest days of church history.

On October 31, 1517, Martin Luther began the Reformation with a declaration that the church must be recalled to the authority of God’s Word and the purity of biblical doctrine.