Are there many devils?

The Catholic Answers

Yes. St. John tells us that Satan was cast out of heaven, and that his angels were thrown down with him. Rev. XII., 9. The devils besought Christ, “If thou cast us out,” Matt. VIII., 31, and said that they were legion. Mk. V., 9.

Radio Replies Volume 1 by Rev. Dr. Leslie Rumble MSC and Rev. Charles Mortimer Carty