'Accuser' in the Bible

oh that I had one to hear me! (behold, here is my signature, let the Almighty answer me); let the accuser write my indictment!

I heard a loud voice in heaven, saying, "Now is come the salvation, the power, and the Kingdom of our God, and the authority of his Christ; for the accuser of our brothers has been thrown down, who accuses them before our God day and night.