"He didn't," Francis replied. "She's been there since before the Duchy was founded. Since before the exodus even. She was put there by none other than Princess Platinum, although I have no idea why. I wouldn't be surprised if nopony knows, including the Lady herself. I can tell you though, that both Twilight Sparkle, and Princess Celestia knew about her, and not only chose to leave her there, but to seal her in even tighter."