Some customs such as VAMPIRES, WEREWOLVES, WITCHES, ZOMBIES, have long been associated with the evil spirit world.
The main Reason behind the costume’s idea is that the Celts wore terrifying masks so that malicious spirits would falsely believe the wearers were spirits and would leave them alone. The church integrated ancient rituals steadily into the feasts of All Souls and All Saints. Later, celebrants went from house to house wearing costumes of saints, angels, and devils. And that’s why we see them heavily as customs people choose for their Halloween Celebration.