Bible specifically mentioned the existence of a devil called Satan, the dragon, and the serpent in Ephesians 6 whether you believe it or not.
Devil has a scheme to destruct God’s children as he did to Adam and Jesus. He is a father of lies, an accuser, and the evil one who keeps deceiving many.
Then how to defeat the schemes of the Devil? Bible says “Put on the full armor of God so that you can take your stand against the devil’s schemes” (NIV, Ephesian 6:11).