"Loose the four angels..."
In verse 13 we see the sixth angel sounding the trumpet, and a voice from the golden altar in heaven tells him to release four angels, "... which are bound in the great river Euphrates..." Thayer's Greek-English Lexicon of the New Testament states that the Greek word which is translated as "bound" in this verse, means, "to bind, fasten with chains, to throw into chains". So we are seeing here, four evil angels who are being restrained. Bear in mind that the abyss, the place of confinement for such angels, was opened by the angel Abaddon (verse 2).
In Jude, verse 6, we read that God has reserved some angels in "everlasting chains" until the day of judgment.
In Revelation 20, Satan himself is bound with a "great chain" and thrown in to the abyss for a thousand years. Jesus glorifies His Father in all that He does. The Beast disgraces his father in that he opened the pit (9:1) into which his father (Satan) will be thrown and held as prisoner.
