It was as Celestia was conducting business that a Royal Guard burst into the throne room. "Your Maj..." he gasped, then stopped before the Sun Throne and began again. "Your Majesty, I bring dire news!"
"What news, Silent Heart?" the Solar Diarch asked.
"Nightmare Moon has returned!" the poor Guardspony gasped.
Eyes widening, Celestia passed the scroll she was writing unto her scribe to finish and then she stood. "Where is she, Silent Heart?"
"She... she's in the morgue." Silent Heart answered promptly. Then, muttering under his breath, "No doubt working some dark ritual upon our honored dead..."
At his answer, Celestia gasped softly, her eyes misting over with tears. There was only one reason why her sister might be there. She hoped, she prayed that it was not to be, but alas... Without hesitation, the Solar Diarch left the Throne Room and made her way to the Palace Morgue. Upon arrival there she entered the heart of the place to find her worst fears come to life. Before her eyes she beheld the Dread Mare, Nightmare Moon, and prepared for a fight... But something was deathly wrong.
Before her was not the Nightmare Moon she knew. This Nightmare Moon sought not to challenge her, sought not to bring upon Equestria Eternal Night. Instead, utter despair suffused Nightmare Moon as she cried and cried and cried... over her beloved. His body, white-haired, wizened... dead. Perfectly washed and prepared for burial. "Oh, Lulu..." the Solar Diarch murmured as she made her way into the room. At the sound, Nightmare Moon whirled about to face the Solar Diarch, flaring her wings and hissing, baring her teeth - desiring nothing more than to protect her beloved human lifemate even in death - but then... she faltered upon seeing Celestia. "He... he adored Us, Celly" said she, struggling to speak through her tears. "Even when We were in this form, he still loved Us all the same; perhaps moreso. But now... n-now..." Squeezing a hoof to her breast, the Dread Mare, choked, gasped, utterly overcome with her grief.
"Wh-When... When did it happen?" Celestia asked. Moving to stand beside the Dread Mare of the Moon - forgetting about the concept of the 'Hero' and the 'Villain' - the Solar Diarch enfolded the black mare with a wing. "At two fifteen this morning," the Lunar Diarch whispered. "We... we felt it; we felt him leave Us... Prepared His body for internment Ourselves..." Lost, insensate, unaware, the jet-black, armored Alicorn gently poked and nosed her beloved David. "We... we do not... understand. He was fine, yesterday; we were having Sup on our Balcony and he was... he was telling me a story from Earth. He was fine, he wasfine, hewas..." A low, keening cry issued forth from deep within her - a sound that almost pushed Celestia over the edge herself - and then, as the Solar Diarch watched, Nightmare Moon sat upon her haunches and begged...
Horror gripped Celestia as Nightmare Moon whimpered, begged, pleaded... - "Please, Celly... please..." - to be undone by the Elements again; for banishment, for death, anything that might undo the wrenching wound within her heart; that she might be with her beloved again...
"I-I..." Celestia stuttered, "I can't, Lulu; you know I can't do that..."
Fueled by her despair, it was then that Nightmare Moon 'fought' with Celestia... if one could even call it a fight. Magical blows, shoving, tussling, horn fencing... all were easily blocked by the Solar Diarch for all had no strength or effort; and even then neither combatant wished to damage the body of dear David. At the end of all things, Nightmare Moon's clumsy attempt at wrestling was turned into the gentlest of embraces and finally, finally she let go, sobbing brokenly 'neath her sister's white wing...
"Sssh..." Celestia soothed, "everything will be alright, Luna..."
"Luna?"
---------------------
"LUNA!"
And then, Luna awakened with a gasp, her ancient heart pounding within her chest with the force of a double edged mallet, to find David - as hale and hearty as the day she'd met him - awake and leaning over her. His eyes were filled with such love, such worry and concern, that she felt as if she'd burst into tears here as she had in her dream!
"Are you alright, love? You were crying out in your sleep?"
"N-No..." choked she, a lump in her throat; then she proceeded to tell him of her awful, awful dream. By the time she'd finished, David was holding her consolingly yet at the same time shaking his head. "Luna..." he chided, gently, "now why would you have a silly dream like that? We shared ourselves with each other the eve we married; since then like you I've been undying - immortal. I'm not going anywhere, love and you can tell Nightie that, too!"
Luna nodded, kiss-kissing his cheeks, blowing softly unto his face. "We know, but... it was still a horrible dream..." Holding his beloved mare close, the human nodded; then his hold became a gentle stroking and scratching here and there as he replied, "I can imagine... but let's make sure you have no more silly dreams, eh?" With those words... suddenly David's hands were everywhere - combing through her mane, roaming over her coat, rubbing her wings and belly... All Luna could do was nicker-laugh helplessly and make other very, very happy pony noises!