Revelation 9:11

9:11 They have as king over them the angel of the abyss, whose name in Hebrew is Abaddon, and in Greek, Apollyon.

Revelation 20:1

The Thousand Year Reign

20:1 Then I saw an angel descending from heaven, holding in his hand the key to the abyss and a huge chain.

Revelation 9:1-2

9:1 Then the fifth angel blew his trumpet, and I saw a star that had fallen from the sky to the earth, and he was given the key to the shaft of the abyss. 9:2 He opened the shaft of the abyss and smoke rose out of it like smoke from a giant furnace. The sun and the air were darkened with smoke from the shaft.

Revelation 11:7

11:7 When they have completed their testimony, the beast that comes up from the abyss will make war on them and conquer them and kill them.

Revelation 17:8

17:8 The beast you saw was, and is not, but is about to come up from the abyss and then go to destruction. The inhabitants of the earth – all those whose names have not been written in the book of life since the foundation of the world – will be astounded when they see that the beast was, and is not, but is to come.