Revelation 5:2

5:2 And I saw a powerful angel proclaiming in a loud voice: “Who is worthy to open the scroll and to break its seals?”

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. ¹ 

Revelation 18:1

Babylon is Destroyed

18:1 After these things I saw another angel, who possessed great authority, coming down out of heaven, and the earth was lit up by his radiance. ² 

Revelation 20:1

The Thousand Year Reign

20:1 Then ³  I saw an angel descending from heaven, holding ⁴  in his hand the key to the abyss and a huge chain.

[9:11]  ¹ sn Both the Hebrew Abaddon and the Greek Apollyon mean “Destroyer.”

[18:1]  ¹ tn Grk “glory”; but often in the sense of splendor, brightness, or radiance (see L&N 14.49).

[20:1]  ¹ tn Grk “And.” Here καί (kai) has been translated as “then” to indicate the implied sequence within the narrative.

[20:1]  ² tn The word “holding” is implied. The two clauses “having the key of the abyss” and “a huge chain in his hand” can be construed in two ways: (1) both are controlled by the participle ἔχοντα (econta) and both are modified by the phrase “in his hand” – “having in his hand the key to the abyss and a huge chain.” (2) The participle ἔχοντα refers only to the key, and the phrase “in his hand” refers only to the chain – “having the key of the abyss and holding a huge chain in his hand.” Because of the stylistic tendency in Rev to use the verb ἔχω (ecw) to mean “hold (something)” and the phrase “in his hand” forming a “bracket” along with the verb ἔχω around both the phrases in question, the first option is preferred.