What are three literary devices used in "Gryphon" by Charles Baxter?

There are so many to choose from! I'll focus on three that I find most salient:

1. Imagery:

"Facing us, she was no special age—an adult is an adult—but her face had two prominent lines, descending vertically from the sides of her mouth to her chin. I knew where I had seen those lines before: Pinocchio. They were marionette lines."

When an author shows you exactly what something looks like, it's imagery. It not only makes for an engaging story but also gives you hints about the characters and/or the theme. The author could have written about any of the thousands of visual details in any real-life scene, especially this one, in a classroom with so many people, but he focuses on this visual image of the teacher's facial lines, which reminds the narrator of a puppet. Why? Probably because the narrator is so stupefied by his dull education that he automatically makes associations to bland, dull, lifeless things that are easily controlled, like puppets.

2. Symbol:

"I bit into my sloppy joe and stared blankly out the window. An almost invisible moon was faintly silvered in the daytime autumn sky."

A symbol in a story is an object (or an event, a color, and so on) that represent more than what it actually is. This adds interest and depth to the story. Here, the boy telling the story, Tommy, is listening to his bizarre and incredible substitute teacher and starting to realize that the world may not be all about facts, that facts may not be as simple as he's been taught. But he hasn't totally figured it out yet. He's just getting a glimpse of it. So, how perfect is it that at that moment, he catches a slight glimpse of the moon in the daytime sky? That moon represents the actual complexity of "facts" for Tommy, who may have just thoughtlessly memorized the fact that the sun shines during the day and the moon comes out at night.

3. Asyndeton:

"I was looking out the window at the farms along County Road H. I knew every barn, every broken windmill, every fence, every anhydrous ammonia tank, by heart."

Asyndeton is when the author purposefully leaves out the connecting words, such as "and." Instead of saying "every barn, every broken windmill, every fence, and every anhydrous ammonia tank," he leaves that word out. The result is that the thought expressed by Tommy right here becomes dramatic, serious, and tense. The asyndeton also helps express the extreme dullness and repetition of events and objects in his life. We hear Tommy thinking in the pattern "thing, thing, thing, thing" and we understand how monotonous his thinking and his life have been up until this point in the story.