The ancient Celtic festival of Samhain is widely considered the precursor to the holiday we all know as Halloween. It marked the end of the summer harvest and the beginning of the winter months, or the dark half of the year. It was crucial at this point in the year to bring in crop stores for the winter months and ensure that livestock were also brought in from the fields and secured for the winter. There are many Irish mythology stories that also revolve around this festival. I will add further posts about Irish myth and folklore in the future.
During this festival, more so than any other time in the year, it was believed by the ancient Celts that the otherworldly beings would mingle with the living. The distance between the two worlds, that of the living and that of the dead, was at its closest point during this festival as well. One of the most popular of the Irish myth creatures is the Fairy. During Samhain they are at the forefront as well, and were often thought to engage in trickery and to even take humans away. The ancient Celts lit huge bonfires to help guide spirits back to the underworld as well as to protect the living from the ghosts, fairies and other demons. As with many ancient festivals, such as those in pre-Christian Ireland like Samhain, a main purpose was to honor the gods and goddesses to ensure a successful year ahead. This success would be realized in the health of ones family, a high crop yield, or plentiful livestock.
When I was in Ireland I was surprised how big of a festival Halloween was there. Now I can see that it is much more rooted in ancient Celtic history and mythology than I could have imagined. At least in Galway, it was celebrated all week-long leading up to the day of Halloween.
Stay tuned for more about Irish mythology.
To Galway and Back 
Very interesting! I had not idea about this. I think I had heard about the fires they lighted but didn’t know it was to lead spirits back to the underworld. Very interesting!