"It was a mirror, smaller than the Magic Mirror: it was circular, with flowers engraved into a square, golden frame."
A mirror acquired by the Evil Queen during her reign, stored in Snow White's Palace until the Huntress steals it and presents it to the Evil Queen. It shows one's true self when one stands before it.
The mirror is mentioned in The Wishing Spell. It is destroyed at the end of the book, when a cannonball hits the room where it is kept during the final battle. This also destroys the Queen's other Magic Mirror.
The Evil Queen looks into the mirror and sees a young woman- Evly, the woman she used to be.
After the mirror is destroyed, Alex catches a glimpse of her reflection in the shards as they flee the collapsing castle. In the mirror, she has a fairy's wings.