Eternal Nightmare: Miasma
A dark chuckle carried on the air. The black alicorn stood majestically with her large wings spread wide. "This night shall last forever!" A white mare flew up behind the dark one.
"Forgive me but I do what must be done. For the kingdom. For Equestria." A beam of rainbow hued magic enveloped the two alicorns. Upon the moon a dark stain looking like a mare's head took shape.
"One day I shall return."
"I pray when my sister returns we will be ready. There is much to be done and I now must walk this path alone. What made her do this?" Celestia had tears in her eyes. She cried for her sister, herself and all the ponies of her kingdom.