What literary term is he would truly be a worm if any of his comrades should see him returning thus the marks flight upon him?

The literary term used in the phrase "he would truly be a worm if any of his comrades should see him returning thus the marks flight upon him" is metaphor.

Here's why:

* Metaphor: A figure of speech that makes an implicit comparison between two things that are not alike, without using words like "like" or "as."

* In this case: "Worm" is being used metaphorically to represent someone who is weak, pathetic, or low-ranking. The speaker is implying that the person's return with "marks of flight" would make him appear cowardly or unworthy in the eyes of his comrades.

The sentence uses the metaphor to create a powerful image and emphasize the shame the person would feel. It suggests that returning defeated would be a devastating blow to his reputation and standing within his group.