"And I will put enmity Between you and the woman, And between your seed and her seed; He shall bruise you on the head, And you shall bruise him on the heel."Advent's seeds, though envisioned in the depths of eternity past, were fist scattered in fragrant Eden moments before Adam and Eve were evicted from paradise.
Believing in the omniscience of the Almighty, I have to believe that even in the deepest mists of the cosmic past, the Trinity that saw the coming rebellion of angels saw that the the chief usurper Lucifer successfully entice our first parents. With this knowledge, They already had a plan to pay the price for the couple's disobedience and redeem humanity from the dark night of eternal death. Which brings us back to this promise in Genesis 3.
Our first parents, standing in the presence of deity and feebly trying to hide behind irritating fig leaves have not only lost their home, but were silently beginning to die. Yet in this, Eve was promised that one of her progeny would face down the progeny of this serpent, defeating it once and for all.
Mel Gibson gave us a powerful, albeit extra-biblical, image of this encounter in his "The Passion of the Christ". In this, Jesus after encountering a viper in Gethsemane, stomps its head and destroys it. The true encounter would occur some hours later on the brutal Roman cross.