Luna stood before her sister, mouth agape, as the white alicorn finished telling her tale. She was at an absolute loss for words. Nothing she'd ever heard before had even come close to what she was hearing now. Shaking her head, she briefly fumbled over her words before managing to speak. "...You succeeded?"
Celestia raised an eyebrow and smiled. "If I hadn't, would I be sitting on my comfy throne right now, talking to my sister?" At that, Luna chuckled wryly.
"Even so, sister, We find it quite interesting that there was a unicorn once that was created entirely from thy mortality." Celestia's face took on a different expression, and she shuffled her hooves like a foal caught in the cookie jar. Luna stared at her for a moment, then slowly spoke. "Sister...even after all this time, I recognize that expression. What did you do?"
Celestia sighed. "Is." Luna stared, uncomprehending. "Is, Luna. There is a unicorn created from my mortality. I...may have gotten slightly attached to her. I gave up a great deal of my raw magical strength to keep her alive indefinitely. She lives in Canterlot under the name Fleur de Lis." Luna continued staring, though this time, disbelieving instead of uncomprehending. After a time, she spoke, and Celestia winced. She knew that voice. That was Luna's 'please tell me you're kidding' voice.
"So, Sister, what thou are saying...is that you gave up a large amount of thy power...to render immortal a pony created from pure mortality?" A soft thump rang through the empty hall as her hoof collided with her face. "Only you, Sister...only you."