The Bottomless Pit
(Rev. 20:1 KJV) And I saw an angel come down from heaven, having the key of the bottomless pit and a great chain in his hand.
The angel with the key shows that God has the power and authority over Satan to bind him into a prison that He has prepared for him. The bottomless pit is the abyss where the evil spirits are held.
(Lk. 8:31 KJV) 31 And they besought him that he would not command them to go out into the deep.
(Rev. 9:1-11 KJV) 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.
The great chain shows the imprisonment. Satan is bound in the abyss before the millennium kingdom.