Answer:
Michael is referring to the Great Deliverance that will be brought by Jesus to the mankind.
Step-by-step explanation:
The given quote is taken from the epic 'Paradise Lost' written by John Milton.
The epic unfolds the biblical account of Genesis and the fall of mankind. In Book 12 of the epic, after the sin and disobedience of Adam and Eve, this incidence takes place. In book 12 of Paradise Lost, angel Michael presents to biblical history to Adam of what will take place and how God will be redeeming mankind from their sins.
Michael in these lines is referring to Jesus who will bring salvation and redemption to mankind. The Seed is referred to Jesus who will come from the womb of a woman. Michael revealed that Jesus will come from the lineage of Abraham and David and will be the Great King. It is Jesus who brought the Great Deliverance to the mankind.