And this is where the dress-up factor came in – costumes and ugly masks were worn to scare away malevolent spirits believed to have been set free from the realm of the dead. This was also known as "mumming" or "guising".

It was believed that at this time the veil between this world and the spirit world was at its thinnest – allowing the spirits of the dead to pass through and mingle with the living. The sacred energy of the rituals, it was believed, allowed the living and the dead to communicate, and gave Druid priests and Celtic shamans heightened perception.