Cross reference
Revelation 20:1
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 1:18
18 and the Living one; and I was dead, and behold, I am alive for evermore, and I have the keys of death and of Hades.
2 Peter 2:4
4 For if God spared not angels when they sinned, but cast them down to hell, and committed them to pits of darkness, to be reserved unto judgment;
Revelation 10:1
1 And I saw another strong angel coming down out of heaven, arrayed with a cloud; and the rainbow was upon his head, and his face was as the sun, and his feet as pillars of fire;
Jude 1:6
6 And angels that kept not their own principality, but left their proper habitation, he hath kept in everlasting bonds under darkness unto the judgment of the great day.
Revelation 9:1-2
1 And the fifth angel sounded, and I saw a star from heaven fallen unto the earth: and there was given to him the key of the pit of the abyss.
2 And he opened the pit of the abyss; and there went up a smoke out of the pit, as the smoke of a great furnace; and the sun and the air were darkened by reason of the smoke of the pit.
Luke 8:31
31 And they entreated him that he would not command them to depart into the abyss.
Revelation 18:1
1 After these things I saw another angel coming down out of heaven, having great authority; and the earth was lightened with his glory.