Foil
Character Role Analysis
Anna/Emery
Representing the sun and moon, Anna and Emery are the book's "astral twins," and their destinies are strangely linked. If you've already read their character summaries, you know that their strange bond means that sometimes one of the "twins" will take on qualities or wounds for the other—for example, when Anna's gun goes off while pointed at her, Emery is the one who ends up with a gunshot wound…even though, as far as we know, he's not in the room.
Understanding Emery and Anna's special relationship, the qualities that they share, and their relationship to the other characters—like how they're each the sun-esque center to the drama that goes on at different points—not only tells us a lot about them, but it's crucial to understanding the structure of the narrative as a whole. For that reason, they're definitely a foil pairing on steroids.