Although Halloween is known with the evil symbols such as carved pumpkins, called jack o lanterns, ghosts, scary monsters, skulls, skeletons, black cats, evil witches, etc., it had nothing to do with evil in its history.
Originally it was an innocent Pagan feast of Celts and they believed that their dead joined them on Samhain, which is the Halloween of our time. As it was the ‘day of deads’ or ‘day of souls’, skull, skeleton and ghost symbols are so normal to be used, but without an evil meaning.
Black cat and witch symbols became a part of Halloween in the Middle Ages. In that period, the black cats were feared by the folk and the black cats were believed to be evil animals. With such a belief, they killed many black cats. The dead bodies of these poor black cats caused the Black Plague in Europe. Millions of people died during the Black Plague.
The Church blamed the witches for the Black Plague. Evil black cats were associated with evil witches. The attack of the church to so-called evil witches was to discourage the folk from applying their pagan habits. In Middle Ages, many people were accused of using magic in evil ways.
As Samhain was also a Pagan feast, the Church declared that demons were coming along with the dead ancestors. The scary monsters and demons would kill the innocent folk on Halloween.