Forgotten: The Precious Sound of Bells

Celestia and Luna travels to the Crystal Empire after hearing about Sombra's chaotic reign of terror upon the pony citizens there. Despite the luck they had on their side, Celestia and Luna end up losing not only the battle between Sombra but also the entirety of the Crystal Empire. Taking their defeat they head back to the castle only to come across a mother and her foal lying alone in the snow. Perhaps a survivor of the Crystal Empire loss? Whatever the situation, the two princesses take the foal in not knowing of it's true nature or even it's roots but perhaps the foal can be a beacon of hope between the relations of pony kind and even the most vicious of beings and most of all teach the princesses themselves an important lesson.