Revelation 12:9

9  And the great dragon was cast out, that old serpent, called the Devil, and Satan, which deceiveth the whole world: he was cast out into the earth, and his angels were cast out with him.

This passage defines who the dragon is. I have heard a well known author say the Devil and Satan are different beings but this passage should make it crystal clear that the dragon, the Devil and Satan are the same. The Devil is not just an evil force or influence as some might think. A specific being was cast out into the earth and the angels that fought with him were also cast out with him. We read in prior verses in this chapter that the number is a third of all the stars (angels). I do not know how many that is but I think it is safe to assume that many millions of angels will be cast out to the earth.  These are beings with incredible power. People on earth will think that the gods have come to earth.  This will lead to the great deception. The millions of other angels that were cast out either will have their own bodies or will possess human ones (maybe this is the real “Invasion of the Body Snatchers”). It will be an incredible time for all those living on the earth.

This verse also tells us about Satan’s nature.  He is the deceiver of the whole earth.  He is a counterfeit god. His work of deception can be seen from his deception in the Garden of Eden until his last deception at the end of the thousand year reign.