In Genesis 3, we meet the antagonist in the biblical account: Satan.  He is a heavenly being who tried to exalt himself above God.  He was cast out of heaven but continues to oppose God in every way possible.  He led the humans to question God's goodness and to play God themselves.  Their rebellion ruptured their relationship with God and disrupted His very good creation, setting up the problem that is the focus of the rest of the Bible.  Yet even in God's cursing of the serpent, there is an allusion to his ultimate plan for restoration.