1 And I saw an angel coming down out of heaven, having the key of the abyss, and a great chain in his hand.
Revelation 20:1 Cross References - JuliaSmith
Luke 8:31
31 And he besought him that he would not command him to go away into the abyss.
2 Peter 2:4
4 For if God spared not the angels having sinned, but delivered up, hurled into Tartarus, to cords of darkness, having been kept for judgment;
Jude 1:6
6 Also the angels not having kept their beginning, but having left their own habitation, he has kept in perpetual chains under darkness for the judgment of the great day.
Revelation 1:18
18 And he living, and I was dead; and, behold, I am living for the times of times, Amen; and have the keys of hades and of death.
Revelation 9:1-2
1 And the fifth angel sounded the trumpet, and I saw a star fallen from heaven to the earth: and there was given to him the key of the well of the bottomless pit.
2 And he opened the well of the bottomless pit; and a smoke went up out of the well, as the smoke of a great furnace; and the sun was darkened, and the air, from the smoke of the well.
Revelation 10:1
1 And I saw another strong angel coming down from heaven, surrounded with a cloud: and a rainbow upon the head, and his face as the sun, and his feet as pillars of fire:
Revelation 18:1
1 And after these things I saw another angel coming down from heaven, having great power; and the earth was enlightened from his glory.