the accuser

D. A. Carson in Scandalous: The Cross and Resurrection of Jesus:

Satan accuses Christians day and night. It is not just that he will work on our conscience to make us feel as dirty, guilty, defeated, destroyed, weak, and ugly as he possibly can; it is something worse: his entire play in the past is to accuse us before God day and night, bringing charges against us that we know we can never answer before the majesty of God’s holiness.

What can we say in response? Will our defense be, ‘Oh, I’m not that bad?’ You will never beat Satan that way. Never. What you must say is, ‘Satan, I’m even worse than you think, but God loves me anyway. He has accepted me because of the blood of the Lamb.’

(via)

Revelation 12:7–12 (ESV);  Satan Thrown Down to Earth 7 Now war arose in heaven, Michael and his angels fighting against the dragon. And the dragon and his angels fought back, 8 but he was defeated, and there was no longer any place for them in heaven. 9 And the great dragon was thrown down, that ancient serpent, who is called the devil and Satan, the deceiver of the whole world—he was thrown down to the earth, and his angels were thrown down with him. 10 And I heard a loud voice in heaven, saying, “Now the salvation and the power and the kingdom of our God and the authority of his Christ have come, for the accuser of our brothers has been thrown down, who accuses them day and night before our God. 11 And they have conquered him by the blood of the Lamb and by the word of their testimony, for they loved not their lives even unto death. 12 Therefore, rejoice, O heavens and you who dwell in them! But woe to you, O earth and sea, for the devil has come down to you in great wrath, because he knows that his time is short!”