Disclaimer: Harry Potter belongs to J.K. Rowling.
A/N: Partly contradicts what JKR said happens to Luna in interviews… because that's the fun of fanfic.
The Greatest Treasure
"Wit beyond measure is man's greatest treasure!"
This was the motto ingrained into Luna Lovegood's ever-so-open mind every day since she was sorted into Ravenclaw at Hogwarts School of Witchcraft and Wizardry.
The Sorting Hat had briefly toyed with the idea of placing her into Gryffindor before ultimately deciding on the House most prized for its intelligence. And though she was often labeled by some of her peers as "gullible" (and by her less polite, more brutish peers as "crazy"), Luna had a Ravenclaw intellect through and through.
"'Wit beyond measure is man's greatest treasure!'" she was known to repeat suddenly, in her strange, dreamlike quality. The quest for knowledge and understanding she held as the highest pursuit, as did her parents, both proud Ravenclaws themselves, or at least, her mother had been a Ravenclaw until she died, when Luna was the age of nine.
Although, her father had told her once—in a whispery, gossipy sort of way, as though imparting a great scandal—that her mother, like herself, had almost been put into Gryffindor, "where dwell the brave at heart".
It was probably this thought that old Xenophilius Lovegood clung to when he took Luna in his arms, teary-eyed, reunited with her for the first time since she had been kidnapped by Death Eaters on the Hogwarts Express.
"I'm sorry," Xenophilius half-sobbed into her hair, after murmuring "My Luna, my Luna…" over and over.
Luna held her father by his shoulders, trying to steady him. "What are you apologizing for, Daddy?"
He looked her in the eyes, and she knew he was thinking of her mother.
"For not being as brave as you. I never was. Even when your dear mother died, God rest her soul, you handled it better than me…."
"Did something happen… while I was gone?"
Fresh tears, shameful ones, brimmed in Xenophilius's eyes, and he told her of the lowest moment of his life, of how in his ultimate weakness he had tried to exchange the lives of her friends for her own.
Luna listened to her father's tale, her protuberant eyes growing all the wider. But she could not pass judgment on her father.
"Voldemort made us do terrible things—all of us—things that we wouldn't normally have done," she said simply.
As Luna allowed herself in her heart to forgive her father, she should have realized then—for his actions were living proof—that wise old Rowena Ravenclaw had gotten it wrong. She didn't learn that till much later—but luckily, Luna was always open to learning.
Home was never quite the same again after the year of Voldemort's defeat. First of all, their house had been destroyed in that freak Snorkack horn explosion—such a rare Snorkack horn meant that particular creature had been of an unusually lucky variety, her father told her. For a while, Luna and her father stayed with the Weasleys, who were very kind, and helped them rebuild their house.
But she didn't have time to see the house completed before it was time to go back to Hogwarts. She ended up leaving the school with exemplary marks on her N.E.W.T.s, including Outstandings in Defense Against the Dark Arts, Care of Magical Creatures, and Herbology (thanks to some tutoring from a close friend).
After school, she traveled a bit, always eager to research a new species for her father's paper, The Quibbler. She had practically taken it over by the time she settled down a few years later. She married later than most of her friends, but the union was no less happy for it.
The revelation about Rowena Ravenclaw came to her suddenly one day as she was harvesting Dirigible Plums in her garden, collecting them in a large, wooden bucket. Her daughter, no more than two years old, sat on her lap, digging in the dirt with a miniature plastic spade, "helping Mommy," as her husband liked to call it. Watching her daughter's natural inquisitiveness—the way she picked out snails from the soil, or the way her eyes widened whenever a gnome popped its head out of a hole—reminded Luna in some small way of her mother, a very intelligent witch who had possessed a superior sense of curiosity.
"We gave you a very appropriate name, then," Luna said dreamily, for Leandra Augusta was partly named for Luna's mother. "You take after her so much. She was such a wonderful witch… smart, but brave, too… I wonder what House you'll be Sorted into…
"Ravenclaw is splendid, but I wonder… perhaps you're headed for Gryffindor… in that case…." Luna bent over to the bush of Dirigible Plums and plucked two of the smaller, orange, radish-like fruits. "You'd better start wearing these right away, to increase your ability to accept the extraordinary. Gryffindors are nice, but some of them can be awfully close-minded," she said, thinking of Hermione Granger and dangling the fruits above her daughter's head as Leandra giggled, grabbing at the brightly colored objects.
Still, Luna thought of Gryffindor with affection. All of her true friends had come out of Gryffindor. They were more accepting of her somehow. No, she wouldn't mind at all if her daughter were placed among that honorable House when the time came for it.
But that was still a long ways away, Luna thought, smiling to herself.
With one last handful dropped into the bucket, she finished collecting the Dirigible Plums—enough for her husband to show to his students in the next day's lesson, for Luna had insisted that they should be a part of any basic Herbology curriculum—and, carrying the bucket in one hand, she gathered Leandra up into her free arm.
"Come, let's go inside now," she said, beginning the trek back up to the castle, "before it turns cold and you catch a Wrackspurt."
And as she held her child close to her heart, making her way home, it suddenly hit her.
"Wit beyond measure is man's greatest treasure."
Rowena Ravenclaw may have been the wisest witch of her age. But Luna knew that she held the greatest treasure of all in her arm.