The Celts had a festival called Samhain, which is where Halloween comes from. For three days, they would have big feasts, light bonfires, and perform rituals. It was a way to thank their gods and prepare for winter. They also believed in an Otherworld with gods and other creatures. Samhain was a time to make these beings happy and keep themselves safe. https://www.ancient-origins.net/news-ancient-traditions-preview/halloween-samhain-0021589