'Bottomless' in the Bible

Then the fifth angel sounded [his trumpet], and I saw a star (angelic being) that had fallen from heaven to the earth; and the key of the bottomless pit (abyss) was given to him (the star-angel).

He opened the bottomless pit, and smoke like the smoke of a great furnace flowed out of the pit; and the sun and the atmosphere were darkened by the smoke from the pit.

They have as king over them, the angel of the abyss (the bottomless pit); in Hebrew his name is Abaddon (destruction), and in Greek he is called Apollyon (destroyer-king).

When they have finished their testimony and given their evidence, the beast that comes up out of the abyss (bottomless pit) will wage war with them, and overcome them and kill them.

“The beast that you saw was [once], but [now] is not, and he is about to come up out of the abyss (the bottomless pit, the dwelling place of demons) and go to destruction (perdition). And the inhabitants of the earth, whose names have not been written in the Book of Life from the foundation of the world, will be astonished when they see the beast, because he was and is not and is yet to come [to earth].

And then I saw an angel descending from heaven, holding the key of the abyss (the bottomless pit) and a great chain was in his hand.

and the angel hurled him into the abyss, and closed it and sealed it above him [preventing his escape or rescue], so that he would no longer deceive and seduce the nations, until the thousand years were at an end. After these things he must be liberated for a short time.