The inscription on the Mirror of Erised comes from the chapter “The Mirror of Erised” in Harry Potter and the Sorcerer’s Stone, American Hardcover Edition (pub. 1997), page 207. It belongs to J. K. Rowling, as do any characters, events or details that you recall from canon. The title of this story was taken from “The Stable Song” by Gregory Alan Isakov.
I show not your face, but your heart’s desire.
He stood before the ornate gold frame, tracing each and every intricately carved letter with his dark brown eyes. He had been down to this room hundreds of times before, and he had long since deciphered the meaning of the strange phrase that decorated the mirror’s edges. It was a testament to his boredom that he had ventured to visit the mirror so many times, never expecting to behold a different vision no matter how many nights he spent standing before it.
But perhaps it wasn’t boredom at all. Perhaps he, in his barely tangible silver form, looking not one day older than twenty-five, simply wished to allow himself to waste away like all other men.
His eyes traced down into the mirror’s shining surface as she finally appeared, the sentient object realizing which of its admirers currently stood before it. He couldn’t resist reaching out and lightly tracing the mirror’s edge as he watched her twirl before him, picking up the hem of her long, featherweight wedding gown as she spun, her heels clicking on a nonexistent dance floor.
The gown had been made especially for her, but she’d never worn it. In fact, she’d returned it to her mother’s team of tailors no less than seven times for alterations, asking that the neck be cut a bit lower, then a bit higher, requesting the addition of pearls at the waist and then immediately having them taken back off. He had endured her for a while, amused by her perfectionism, but then she took off into the forest with the tiara she should have worn and he knew the truth at last.
The jeweled crown adorned her rich dark locks now, the sapphires embedded in the white gold frame glittering at him, taunting him with the life he might have had in some other universe. But he felt no bitterness, no anger. None remained in him after what he spent that fateful evening.
She turned to face him and he could have sworn that he felt his heartbeat jump to life, quickening rapidly until it achieved an unnatural pace. Her beautiful blue eyes glittered with the joy of a new bride, a perfect compliment to the easy smile that resided upon her face with its other fair features. She was looking at him and beckoning him to join her, and he almost stepped forward.
His feet did not touch the floor. He looked down, ashamed that the mirror had so easily deluded him once more, entertaining him with a fantasy that would never come to life. He could never step in time with her, for neither of them inhabited mortal bodies. He had no heart left to beat.
Another man ambushed him, approaching out of the nothingness of the mirror’s surface, capturing the delicate fingers of the woman and moving her about in an elegant waltz.
He had not seen his corporeal form in many weeks; the Fat Friar had employed all of the ghosts to help Professor Flitwick decorate the Great Hall for the closing feast, and between that duty and his personal job of helping to keep Peeves the poltergeist in line, he hadn’t been to visit the mirror since the last depressing passing of the anniversary of his birth. He took his eyes off the beauty of his bride-to-be for just a moment and tried to remember looking as happy as this man.
The man in the mirror wore a ceremonial blue coat emblazoned with the medals of a war hero, a young second lieutenant who had seen a few significant battles but managed to avoid serious injury. Atop his fair hair sat a coronet inlaid with six identical white pearls, and around his neck hung a gold locket that bore a large ‘S’ formed with minute emeralds, a loan from his uncle. Amidst all these jewels, however, the broad smile on his face, which matched that of his new wife, outshone each and every piece.
He stood there in the darkness, rooted to the spot, knowing what was coming next but unable to avoid it, unable to simply turn away and break the mirror’s spell. The light with no source glinted off the sapphires in the tiara, tracing along the groom’s war medals and flashing back at him at last, illuminating the deep scarlet stains on the front of his aged shirt for a mere moment.
The man in the mirror dipped the bride gently and kissed her lips, and he fell to his knees.
He couldn’t stare at her any longer, not as long as he had the terrible knowledge that what she became was not who she was meant to be. Neither of them had the chance, not after what he did, not after the two lives he took on that cursed evening. The bloodstains were deceivingly fresh.
But no, it was her, at least somewhat her fault. He had never seen the magnificent smile she wore in the mirror, placid and blissful, but he had seen something like it when they were younger. That was many years ago, though, too many to count. The last smile she’d given him… it was colder.
He glanced up in time to catch her eyes, to see that wicked tiara twisted up in her long hair.