In satan who is an active spirit with an intellect and a will. His function is to oppose God by attacking the people of God through temptation, confusion, disbelief, and evilness.

John 8:44
You belong to your father, the devil, and you want to carry out your father's desire. He was a murderer from the beginning, not holding to the truth, for there is no truth in him. When he lies, he speaks his native language, for he is a liar and the father of lies.

I Peter 5:8
Be self-controlled and alert. Your enemy the devil prowls around like a roaring lion looking for someone to devour.

I John 3:8
He who does what is sinful is of the devil, because the devil has been sinning from the beginning. The reason the Son of God appeared was to destroy the devil's work.

Luke 8:12
Those along the path are the ones who hear, and then the devil comes and takes away the word from their hearts, so that they may not believe and be saved.