I saw an angel coming down from heaven, having in his hand the key to the abyss and a great chain in his hand. And he seized the dragon, the serpent of old, the one who is the devil and Satan, and bound him for a thousand years, and he threw him into the abyss and locked and sealed it over him, in order that he might not deceive the nations any longer until the thousand years were completed; after these things it is necessary for him to be loosed for a little while.

And I saw the thrones, and they sat upon them, and judgment was given to them. And [I saw] the souls of those beheaded because of the testimony of Jesus and because of the Word of God, and those who did not worship the beast nor his image and did not receive the mark upon their foreheads and upon their hands; and they came to life and reigned with Christ for a thousand years. (The rest of the dead did not come to life until the thousand years were completed.) This is the first resurrection. Blessed and holy is the one who has a part in the first resurrection; over these the second death does not have authority, but they will be priests of God and Christ, and they will reign with Him for the thousand years.

And when the thousand years are completed, Satan will be loosed from his prison, and he will go out to deceive the nations who are in the four corners of the earth, Gog and Magog, to gather them for the battle, whose number is as the sand of the sea. And they went up to the breadth of the earth and surrounded the camp of the saints, namely, the beloved city, and fire came down from heaven and devoured them. And the devil who deceived them was thrown into the lake of fire and sulphur where both the beast and the false prophet were, and they will be tormented day and night for ever and ever. Revelation 20: 1-10

In Revelation 19, at the Second Coming, the beast and the false prophet are captured and destroyed in the lake of fire. And the unrepentant wicked are slain and await their final judgment. John now sees, in chap. 20, an angel descending from heaven with a key and chain. The key and chain are figurative terms that denote the divine authority and power behind the angel being able to seize Satan. With the figurative chain and key, the angel binds Satan, throws him into the abyss, and seals the abyss for a thousand years.

The word “abyss” is first used in Genesis 1: 2. The word refers to the earth as being in a chaotic condition before the creation. In the New Testament, the abyss (or bottomless pit) is described as a dark and chaotic abode of demons under God’s control (Luke 8: 31; 2 Peter 2: 4; Revelation 9: 2, 3).

Here, in the context of Rev. 20, the abyss implies the whole of the earth as being in a chaotic condition, what with the devastation of the seven last plagues and the geographical breakup that occurs at the Second Coming. Desolated and uninhabited, the earth becomes an abyss, much like its condition before creation. This is the bound circumstance in which Satan, along with his angels, finds himself figuratively chained and imprisoned. For a thousand years (the millennium), Satan is limited to this world, and so is his power to deceive; for during this period, there aren’t any humans alive on earth.

During the millennium, John also sees what is taking place in heaven. The saved people of God are sitting on thrones. Included in this redeemed group are those who were slain for their faithfulness to Jesus’ testimony and God’s Word. Also seen in the group are those who didn’t worship the beast nor receive his mark. Altogether, this group of the saved are those living and translated, and those called from the grave at the Second Coming, which triggers the first resurrection. All sitting on the thrones are blessed, for they are not subjected to the second death, which is eternal death brought on by the lake of fire.

The group is also blessed and made holy as kings and priests of God and of Christ, and they will reign with Him in heaven during the millennium and throughout eternity. This is the fulfillment of Christ’s promise that the overcomers would share His throne (Rev. 3: 21).

As kings and priests, judgment is given to the group. Paul wrote about this when He said the time is coming when the saints will judge both the world and angels (1 Corinthians 6: 2, 3). The judgment given them is in terms of examining the fairness of God’s decisions concerning the lost, both human and angelic.

John’s attention is then directed to the close of the millennium. At that point, apparently New Jerusalem has already descended from heaven (explicitly stated in Rev. 21: 9, 10). The second resurrection takes place, and the wicked dead rise from their graves. That, in effect, loosens Satan from his imprisonment. Once again, he is able to deceive the nations from every corner of the earth: north, east, south, and west; in other words, the whole world.

Because the nations are in revolt against God, with the intention to invade God’s people in New Jerusalem, John figuratively labels the nations with the names of Gog and Magog. In the Old Testament, Gog is a prince from the land of Magog (Ezekiel 38: 1, 2), which invaded God’s people in Israel. Additionally, Jewish tradition equates Gog and Magog with the nations that rebelled against God and His Messiah in Psalm 2.

It has been suggested that Satan is able to deceive the nations with the lure of immortality. Inside the New Jerusalem, is the tree of life. (Rev. 22: 2). Satan leads the wicked into believing that they can seize the city and then be able to partake of the tree of life so that they too may get to live forever.

Anyway, however he does it, Satan persuades the nations to surround New Jerusalem in order to attack it. Before that happens, God intervenes with a fire from heaven that devours the nations (a more detailed description of their fate is in verses 11-15). Then Satan, himself, is thrown into the lake of fire, which burns as a sea of flames on the surface of the earth, resulting in its purification. In this divine eternal fire, originally prepared for the devil and his angels (Matthew 25: 41), Satan and all who side with him are ultimately destroyed.

That the phrase “tormented day and night forever and ever” is used is a restatement of the language used in Rev. 14: 10, 11. In reference to these verses, the phrase, “forever and ever,” does not mean an indefinite eternity of burning. For instance, although Sodom and Gomorrah were lit with eternal fire, that fire doesn’t burn today. The purpose of fire is to consume, not to preserve. Eternal fire lasts long enough to completely consume with nothing left to be burned. In other words, in this case, “forever and ever”  is the final effect of God’s purpose – the end of sin and sinners – that makes the fire eternal. Read Hell-Fire for more on the topic.