That's an image of art ultimately leading out of art to a kind of state of de-sublimation.

这一艺术的形象最终走出了,艺术走向去崇高化。

耶鲁公开课 - 现代诗歌课程节选

The simile is there ostensibly to compare Satan with the great sea beast, leviathan. In the comparison of Satan's shield with the moon is the figure of the Tuscan artist, the Tuscan artist being Galileo.

这个明喻很明显是将撒旦和凶猛的海中野兽利维坦，进行了对比，在把撒旦的庇护和月亮的比较之中,突出了那个托斯卡纳艺术家的形象，伽利略。

耶鲁公开课 - 弥尔顿课程节选