A fifth trumpet sounds. A star falls to earth. The star is given a key to unlock the abyss. (Not a good idea.) A sixth trumpet releases the four angels bound at the Euphrates. In this teaching from Revelation 9, we learn about who is in the abyss and we meet the hosts of Abaddon.
Naked is Sheol before Him, and Abaddon has no covering. (Job 26:6)
Sheol and Abaddon lie open before the LORD, how much more the hearts of men! (Proverbs 15:11)