While commissioned to illustrated the Bible, Blake created his iconic “Great Red Dragon” series, depicting four scenes from the Book of Revelation. This one corresponds to chapter twelve, which begins:
“And there appeared a great wonder in heaven; a woman clothed with the sun, and the moon under her feet, and upon her head a crown of twelve stars: And she being with child cried, travailing in birth, and pained to be delivered. And there appeared another wonder in heaven; and behold a great red dragon, having seven heads and ten horns, and seven crowns upon his heads. And his tail drew the third part of the stars of heaven, and did cast them to earth: and the dragon stood before the woman which was ready to be delivered, for to devour her child as soon as it was born.” [Rev 12:1-4]
The dragon is normally identified with Satan; the woman with Israel and the Church.