“And I saw an angel come down from heaven, having the key of the bottomless pit and a great chain in his hand.”
King James Version (KJV)
20:1 And I saw an angel decending out of heaven - Coming down with a commission from God. Jesus Christ himself overthrew the beast: the proud dragon shall be bound by an angel; even as he and his angels were cast out of heaven by Michael and his angels. Having the key of the bottomless pit - Mentioned before, #Rev 9:1|. And a great chain in his hand - The angel of the bottomless pit was shut up therein before the beginning of the first woe. But it is now first that Satan, after he had occasioned the third woe, is both chained and shut up.
Re 20:1 The Millennium SUMMARY OF REVELATION 20: Satan Bound for a Thousand Years. Thrones and Saints Reigning with Christ. The First Resurrection. Satan Loosed at the End of a Thousand Years. The Gathering of Gog and Magog and of the Nations. Their Attack Upon the Saints. Their Destruction. The Devil Cast into the Lake of Fire. The Great Judgment. And I saw an angel come down from heaven, having the key of the bottomless pit. "Having the key of the abyss" (Revised Version). The abyss is named in Re 9:1,11 11:7 17:8. It is the present abode of Satan and his evil spirits. The things seen by John are symbolical. They imply that in some way the power of Satan shall be virtually destroyed upon the earth. And a great chain in his hand. See PNT "Re 20:2".