Bottomless Pit

Bottomless pit is “Tartarus” in Greek. It is also often refered to as hell.

Condition in bottomless pit

Fallen angels are in darkness and chained. There is smoke, a great furnace, and there are creatures like big locusts.

Jude 1:13
_{¹³ Raging waves of the sea, foaming out their own shame; wandering stars, to whom is reserved the blackness of darkness for ever.}

2 Peter 2:4
_{⁴ For if God spared not the angels that sinned, but cast them down to hell, and delivered them into chains of darkness, to be reserved unto judgment;}

Jude 1:6
_{⁶ And the angels which kept not their first estate, but left their own habitation, he hath reserved in everlasting chains under darkness unto the judgment of the great day.}

Revelation 9:2-3
_{² And he opened the bottomless pit; and there arose 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.
³ And there came out of the smoke locusts upon the earth: and unto them was given power, as the scorpions of the earth have power.}

Until when they are there?

Angels that sinned are stuck in the bottomless pit until judgment day

Jude 1:6
_{⁶ And the angels which kept not their first estate, but left their own habitation, he hath reserved in everlasting chains under darkness unto the judgment of the great day.}

2 Peter 2:4 
_{⁴ For if God spared not the angels that sinned, but cast them down to hell, and delivered them into chains of darkness, to be reserved unto judgment}

Do the creatures casted there like or fear going in the bottomless pit?

They beg God not to put them there

Luke 8:26-39
_{²⁶ And they arrived at the country of the Gadarenes, which is over against Galilee.
²⁷ And when he went forth to land, there met him out of the city a certain man, which had devils long time, and ware no clothes, neither abode in any house, but in the tombs.
²⁸ When he saw Jesus, he cried out, and fell down before him, and with a loud voice said, What have I to do with thee, Jesus, thou Son of God most high? I beseech thee, torment me not.
²⁹ (For he had commanded the unclean spirit to come out of the man. For oftentimes it had caught him: and he was kept bound with chains and in fetters; and he brake the bands, and was driven of the devil into the wilderness.)
³⁰ And Jesus asked him, saying, What is thy name? And he said, Legion: because many devils were entered into him.
³¹ And they besought him that he would not command them to go out into the deep.}

Is the bottomless pit locked?

It’s probably locked because according to the book of Revelation, there is a key for the bottomless pit.

Revelation 20:1
_{1 And I saw an angel come down from heaven, having the key of the bottomless pit and a great chain in his hand.}

Revelation 9:1-2
_{1 And the fifth angel sounded, and I saw a star fall from heaven unto the earth: and to him was given the key of the bottomless pit.
² And he opened the bottomless pit;}

Who is in bottomless pit exactly ?

Angels that sinned were casted and are stuck in the bottomless pit.  The dragon, that old serpent, which is the Devil, and Satan, big locusts like creatures, and the kings of the locusts king over them, which is the angel of the bottomless pit, whose name in the Hebrew tongue is Abaddon, but in the Greek tongue hath his name Apollyon.

◾fallen angels

Jude 1:6
_{⁶ And the angels which kept not their first estate, but left their own habitation, he hath reserved in everlasting chains under darkness unto the judgment of the great day.}

2 Peter 2:4  (maybe not here)
_{⁴ For if God spared not the angels that sinned, but cast them down to hell, and delivered them into chains of darkness, to be reserved unto judgment;}

Revelation 20:1-3, 7
_{1 And I saw an angel come down from heaven, having the key of the bottomless pit and a great chain in his hand.
² And he laid hold on the dragon, that old serpent, which is the Devil, and Satan, and bound him a thousand years,
³ And cast him into the bottomless pit, and shut him up, and set a seal upon him, that he should deceive the nations no more, till the thousand years should be fulfilled: and after that he must be loosed a little season.
⁷ And when the thousand years are expired, Satan shall be loosed out of his prison,}

◾Abaddon, apollyon, bottomless pit angel and his locusts

Revelation 9:1-11
_{1 And the fifth angel sounded, and I saw a star fall from heaven unto the earth: and to him was given the key of the bottomless pit.
² And he opened the bottomless pit; and there arose 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.
³ And there came out of the smoke locusts upon the earth: and unto them was given power, as the scorpions of the earth have power.
⁴ And it was commanded them that they should not hurt the grass of the earth, neither any green thing, neither any tree; but only those men which have not the seal of God in their foreheads.
⁵ And to them it was given that they should not kill them, but that they should be tormented five months: and their torment was as the torment of a scorpion, when he striketh a man.
⁶ And in those days shall men seek death, and shall not find it; and shall desire to die, and death shall flee from them.
⁷ And the shapes of the locusts were like unto horses prepared unto battle; and on their heads were as it were crowns like gold, and their faces were as the faces of men.
⁸ And they had hair as the hair of women, and their teeth were as the teeth of lions.
⁹ And they had breastplates, as it were breastplates of iron; and the sound of their wings was as the sound of chariots of many horses running to battle.
¹⁰ And they had tails like unto scorpions, and there were stings in their tails: and their power was to hurt men five months.
¹¹ And they had a king over them, which is the angel of the bottomless pit, whose name in the Hebrew tongue is Abaddon, but in the Greek tongue hath his name Apollyon.}

What is bottomless pit exactly?

Bottomless pit seems to be like a prison for fallen angels.

Revelation 20:7
_{⁷ And when the thousand years are expired, Satan shall be loosed out of his prison,}

Ezekiel 31:16 (Hell in this is Sheol in ESV but mentioned pit)
_{¹⁶ I made the nations to shake at the sound of his fall, when I cast him down to hell with them that descend into the pit: and all the trees of Eden, the choice and best of Lebanon, all that drink water, shall be comforted in the nether parts of the earth.}