This is an intriguingly ambivalent portrayal of a snake. Wright manages to convey an impression that the snake is both strikingly important as well as nothing much to worry about.
Devices: In the image of the "sun glazed [on] his curves of diamond scale," Wright seems to emphasise the snake's special, regal qualities through her use of the diamond metaphor. The snake glitters mesmerisingly before the speaker's eyes. She also uses alliteration at several points to dramatise the snake's authority, such as in the phrase, "food / fled living from his fierce intent". The alliterative words here fall on strongly stressed syllables which gives a sense of the snake's power. Wright finishes with a pointedly nonchalant tone as they "took a deeper breath of day, / looked at each other, and went on."
Word Choices: The snake comes across as an invasive and arresting threat comparable to the famous serpent in the Genesis story in The Bible, especially in the contrast Wright's words make between the walkers' calm, warm world and the snake's active, cold one. The sibilant words in the opening line, "Sun-warmed in this late seasons' grace", establishes a relaxed warm mood which the snake penetrates: it "froze" the walkers mid-stride. In addition, the word "Cold" has a heavy effect at the start of the final stanza, which leaves a final impression of the snake's potent presence. However, unlike the biblical snake, this one ultimately fails to gain dominance over the walkers.