The prophecy in Genesis 3:15 says that One would come to destroy the head of the Serpent. In Revelation 13:3 we find that one of the heads of the Beast was wounded to death, but his deadly wound was healed; and all the world wondered after the beast.
Here God is giving a description of how Christ defeated Satan at the cross. Since His birth, Satan’s purpose was to destroy Christ. Satan didn’t know, and much less expected that Christ was going to live again. He thought that Christ was terminated at the cross.
But, Christ went to Hades, took his people from the dominion of Satan and rose again victorious. Now, Christ has the key of death and Hades, and Satan has no power against God’s people. Still, he has a kingdom for the present time. He still continue deceiving the nations.
Satan is deadly wounded, and cannot do anything against God’s people; but he will continue deceiving the world until Christ comes again.