What is the Abyss in Revelation 9:1? 

The word abyss (ἄβυσσος) refers to an “immensely deep space” (BDAG) and sometimes refers to the place of the dead in the Old Testament and other Second Temple Jewish literature. But this “bottomless pit” is more often associated with fallen angels and demonic forces.

In Revelation 9:1 the angel has “the key to the shaft of the abyss” (ἡ κλεὶς τοῦ φρέατος τῆς ἀβύσσου), although this is often translated as “the bottomless pit.” Both the word “shaft” and “Abyss” have articles in the Greek indicating they are well-known to the readers. The word appears seven times, all but twice with reference to a “three tied cosmology,” the angel descended from heaven to earth and then opened the gate of the underworld (Aune 2:525).

The Septuagint translates the Hebrew (thwm, תְּהוֹם) in Genesis 1:2 as ἄβυσσος, “darkness was on the face of the deep.” The chaotic waters are often associated with dark forces in both the Old testament and the literature of the Ancient Near East. For example, in Psalm 77:16, the waters of the deep (תְּהוֹם, ἄβυσσος) tremble when they see the Lord. In LXX Job 38:16 “have you seen the gates of deep darkness (ἀβύσσου)?” is in parallel to “the gates of Hades (πυλωροὶ ᾅδου) in 38:17. In Psalm 71:20 the deep is the place of the dead, “from the depths of the earth, you will bring me up again.”

Although Luke 8:31 implies demons are imprisoned in the abyss, there is nothing in Revelation that specifically states the abyss is a place of torment. This is the view of Second Temple period literature (compare also 2 Peter 2:4 and Jude 6).

1 Enoch 18.11–14 And I saw a deep pit with heavenly fire on its pillars; I saw inside them descending pillars of fire that were immeasurable (in respect to both) altitude and depth. 12 And on top of that pit I saw a place without the heavenly firmament above it or earthly foundation under it or water. There was nothing on it—not even birds—but it was a desolate and terrible place. 13 And I saw there the seven stars (which) were like great, burning mountains. 14 (then) the angel said (to me), “This place is the (ultimate) end of heaven and earth: it is the prison house for the stars and the powers of heaven.

1 Enoch 10.13–14 And against his angels whom he had sent to the earth he was very angry. He commanded that they be uprooted from all their dominion. And he told us to bind them in the depths of the earth, and behold, they are bound in the midst of them, and they are isolated.

Jubilees 5:6 And against his angels whom he had sent to the earth he was very angry. He commanded that they be uprooted from all their dominion. And he told us to bind them in the depths of the earth, and behold, they are bound in the midst of them, and they are isolated.

In the Animal Apocalypse, the fallen stars are punished by “binding his hands and feet and throwing him into an abyss—this abyss was narrow and deep, empty and dark” (1 Enoch 88:1). In 1 Enoch 90:

1 Enoch 90.24–27 Then his judgment took place. First among the stars, they received their judgment and were found guilty, and they went to the place of condemnation; and they were thrown into an abyss, full of fire and flame and full of the pillar of fire. 25 Then those seventy shepherds were judged and found guilty; and they were cast into that fiery abyss. 26 In the meantime I saw how another abyss like it, full of fire, was opened wide in the middle of the ground; and they brought those blinded sheep, all of which were judged, found guilty, and cast into this fiery abyss, and they were burned—the abyss is to the right of that house; 27 thus I saw those sheep while they were burning—their bones also were burning.

After Asenath’s conversion, she describes her experience as a rescue from darkness and the “foundations of the abyss”:  “Blessed be the Lord your God the Most High who sent you out to rescue me from the darkness and to bring me up from the foundations of the abyss, and blessed be your name forever” (Joseph and Aseneth 15.12).

In Revelation 9, the Abyss or bottomless pit is the source of the demonic locust-like creatures. Later in Revelation the beast rises from the sea (11:7; 17:8) and the abyss will be the place of Satan’s imprisonment during the 1000-year kingdom (20:1-3)