Revelation 20:7-8

 "And behold, I am coming quickly. 

Blessed is he who heeds the words of the prophecy of this book."     

Revelation 22:7  NASB

When the thousand years are over, Satan will be released from his prison and will go out to deceive the nations in the four corners of the earth--Gog and Magog--and to gather them for battle. In number they are like the sand on the seashore. 

When the thousand years are over, Satan will be released from his prison and will go out to deceive the nations 
Revelation 20:3  He threw him into the Abyss, and locked and sealed it over him, to keep him from deceiving the nations anymore until the thousand years were ended. After that, he must be set free for a short time.
Revelation 20:10  And the devil, who deceived them, was thrown into the lake of burning sulfur, where the beast and the false prophet had been thrown. They will be tormented day and night for ever and ever. 
Revelation 12:9  The great dragon was hurled down--that ancient serpent called the devil, or Satan, who leads the whole world astray. He was hurled to the earth, and his angels with him.

in the four corners of the earth 
Isaiah 11:12  He will raise a banner for the nations and gather the exiles of Israel; he will assemble the scattered people of Judah from the four quarters of the earth.
Ezekiel 7:2  "Son of man, this is what the Sovereign LORD says to the land of Israel: 'The end! The end has come upon the four corners of the land!' "
Revelation 7:1  After this I saw four angels standing at the four corners of the earth, holding back the four winds of the earth to prevent any wind from blowing on the land or on the sea or on any tree.

Gog and Magog 
Ezekiel 38:2-3  "Son of man, set your face against Gog, of the land of Magog, the chief prince of Meshek and Tubal; prophesy against him and say: 'This is what the Sovereign LORD says: I am against you, Gog, chief prince of Meshek and Tubal.' "
Ezekiel 39:1  "Son of man, prophesy against Gog and say: 'This is what the Sovereign LORD says: I am against you, Gog, chief prince of Meshek and Tubal.' "

and to gather them for battle 
Revelation 16:14  They are demonic spirits that perform signs, and they go out to the kings of the whole world, to gather them for the battle on the great day of God Almighty.

In number they are like the sand on the seashore 
Ezekiel 38:9  " 'You and all your troops and the many nations with you will go up, advancing like a storm; you will be like a cloud covering the land.' "
Ezekiel 38:15  " 'You will come from your place in the far north, you and many nations with you, all of them riding on horses, a great horde, a mighty army.' " 
Hebrews 11:12  And from this one man (Abraham), and he as good as dead, came descendants as numerous as the stars in the sky and as countless as the sand on the seashore.

(parentheses are mine)

Scriptures taken from the Holy Bible, New International Version® NIV®, Copyright© 1973, 1978, 1984, 2011 by Biblica, Inc.® Used by permission. All rights reserved worldwide. 
Limited to 15 verses per post.