It is well known that spirits of the dead come back on this night, searching for someone to possess the following year.
Celtics thought that during this night, all phisical laws could be stopped. There was no more time, nor space laws, the world of the alive and the world of the dead became one thing.
Of course living people did not want to be possessed! Therefore people living in the villages in that night made their houses cold and unfriendly, they did not light the fire, they made their bodies look horrible.
They would use monster masks and they would go around the village scaring to death all the spirits they would meet.
