1 Corinthians 10:20-21
[Certainly not!] But I am saying that the Gentile sacrifices are [really] offered to evil spirits and not to God. And I do not want you to have fellowship with evil spirits.
1 Timothy 4:1
Now the Holy Spirit specifically says that in later times [Note: "Later times" in the New Testament usually refers to the period following the first coming of Christ and the establishment of the church], some people will fall away from the faith [i.e., the true teaching of Christianity]. They will pay attention to deceitful spirits [i.e., lying people] and the teaching of evil spirits.
Revelation 16:14
For they are spirits of demons, which perform [supernatural] signs. These spirits go out to the kings of the whole world to assemble them for battle on the great day of Almighty God.