Hardly enough could be said about Gen 3:15. It is the seed bed, not only of the gospel but of the whole comprehensive mystery of God that is finished with the 7th trumpet (Rev 10:7). The two seeds establish the two lines of men by which the plan of redemption can be traced from beginning to end. It is more than Messiah and Satan. It anticipates the line of the ungodly making up the city of man, mystery Babylon, and the line of the children of the Spirit who are headed up in the Messiah who form corporately the city of God, the heavenly Zion.