Before Luna flashed a wall of color, circling her nightmare-induced body. She screamed––not in anger, but in fear. The Elements would send her back to her prison in the moon. Equestria and her sister would reject her forever this time through these new bearers of the Elements of Harmony.
She stopped screaming and braced herself for a powerful throw into heaven and was about to close her eyes when the colors began flashing brighter than before. Luna peered at the flashes, and then through them. She saw Equestria open up before her. She saw Celestia high on castle a balcony, far above Equestria, bowing her head as she lowered the sun. Luna peered at the white alicorn mare, a being she had not seen for a thousand years, with both longing and dread.
Luna tried to be angry, but she saw tears in Celestia's eyes. The light of the Elements suddenly closed in around her. It was not the rough grip that would toss her into banishment, but an embrace that silently begged her to return to harmony. The anger vanished in an outpouring of peace, and Luna chose not to force anger back as she realized the Elements were granting her a second chance.
This could be her chance to live again!
Next came pain. Shredding, splintering pain. The rainbow light of the Elements tore through the shell of Nightmare Moon that had ensconced Luna for far too long, a nightmare representation of her resentment, jealousy, and anger. Luna gritted her teeth, scream gone as she accepted the pain. She had earned it. She would take it if it meant getting her sister and Equestria back!
The Elements sensed her intent, and through the pain she felt a wash of relief. The nightmare that had infused itself into the very fibers of her body was being washed away.
Luna almost didn't register the feeling of her body sprawled on the floor, half unconscious as she tried to regain control of her limbs and head. She managed to register her light-blue coat and cobalt blue mane, and how scrawny and thin her body had become. Her crown and other vestments, heavy things made of black and blue meteorite she had once borne with graceful ease, felt too big and weighty for her now.
"Princess Luna."
Her eyes opened and her soul leaped at the voice. Then all at once she cringed and looked away from the white glow approaching her. The remnants of Nightmare Moon drifted away from her in a cloud of dust that smelled of smoke. Luna trembled as Celestia knelt before her, heard her loving reprimand, heard her plea of friendship, and knew she had been forgiven of all past grievances against her sister. They embraced, and Luna felt tears as warm as sunlight dampen her coat.
In the excitement of the new day, Luna traveled with her sister to bring the ponies of Harmony back to Ponyville.
After the carriage left Ponyville and took to the sky, Luna's weakened body collapsed onto her stomach, her wreath of welcome roses falling from her neck. Celestia lowered her head near her in concern.
"I'm sorry, sister," Luna murmured. "I'm so tired. So very tired."
"I understand," Celestia whispered. She barked a command to the chariot pegasi, resting one leg over Luna.
Celestia did not completely understand. She didn't understand that Luna hadn't slept a day or night since she was banished. Her rage and envy had driven her into a perpetual wakefulness. Every moment had been spent dwelling on plans of vengeance, or on memories, or on trying to break free from her prison. She had let her life she had chosen become a living nightmare, and now that Nightmare Moon was gone, her body, though immortal, screamed for rest.
The chariot veered towards the mountains central to the landscape. Upon the face of the largest mount was a great and colorful city humming with life. Pegasi and airships glided through its airspace, and Luna smelt foods and spices and the multitudes of ponies within. She wanted to ask what this place was, but even her jaw hung slack as she let her eyes close.
Instead of heading straight towards the city, their pegasi flew them up the flank of the mountain until they came to a platform looked over by a single two-story building. A narrow road led into a crevasse and to the city.
"Luna, you must walk one more time," Celestia told her. Luna, willing to please her sister in any way, forced her legs under her. Celestia hopped from the chariot, and as Luna stepped down, her taller sister pressed herself against Luna, and the Princess of the Moon gratefully leaned her weight against her.
Side-by-side, the Princesses followed the pegasi guards down the crevasse. Luna's head hung low, and she distantly heard the clang and clank of her horseshoes and those of Celestia's, and the heavy clip-clop of the guards' hooves. They echoed against the rocks and kept Luna awake.
She became aware of a door in the cliff, which they filed through. Celestia provided a ball of light from her horn to light the way. At this point Luna navigated by feeling where her sister was at her side. They emerged from the corridor into a hall with sunlit, stained glass windows. Nopony else appeared to be present.
Celestia ordered the guards to guide them to her personal chamber. Luna groaned inwardly when they faced stairs, but she urged herself up them to keep up with Celestia. Luna realized she was sweating, and damp locks of her light blue mane hung across her eyes. She smelled horrible too, as she had not bathed for a thousand years, and she abruptly pulled away from Celestia.
"I'm sorry," she managed to mutter. Celestia gazed at Luna with her big pink eyes and smiled. She unfurled her near wing and gently pulled Luna back to her side.
"I'll have a warm bath prepared," she said. "Do you still enjoy lavender salts?"
Luna nodded, and Celestia gave a muffled, pleased whicker. Luna smiled and tried to lift her head and take in more of the castle.
It was even more grand than their first castle, with longer halls and more windows. Instead of gray stone, Celestia had chosen white marble and granite for the floors and walls. Everywhere, from windows to arch key-stones to tapestries, were symbols of the sun overlaid with a crescent moon. Even in Luna's absence, it seemed Celestia had made it a point that ponies remember the moon as well as the sun. As they passed more depictions of the moon and sun, Luna felt more and more welcome in that new place.
Her exhaustion caught back up to her in a wave when they approached a spiral stairway, the last stairway before Celestia's room. Luna's legs quivered at the aspect of going up those stairs, but she snorted at her own weakness and began to climb. Celestia watched her progress for a few steps, nodded to the guards, and followed Luna.
The guards remained below. Celestia caught up to Luna, and together they came into an ante hall, and then entered the door at the other end.
A smell of roses drifted across them. Luna's nostrils flared, and her eyes rolled around to take in the spacious rotunda. A rainbow of glass windows circled the chamber, with a high-post bed against one wall under a window depicting the moon and sun. One doorway led to a small room with bookshelves, another to a powder room, and the last to a balcony.
Luna's eyes turned down to a pony who stood by one of the window curtains. It was a unicorn mare with a light yellow coat and a curled white mane and tail. Her mark of adulthood––or cutie mark, as ponies now referred to them––was of three folded napkins. The pony stared at Luna, pupils dilating.
"This is my pony-in-waiting, Gentle Fold," Celestia explained. "Gentle, this is my sister, Princess Luna. Attend to her every need as you would to me...although I will be attending her today."
Gentle Fold visibly jumped, and then nodded. Luna sighed and turned away, more interested in sleep.
"My pillow is yours, sister," Celestia said with a deferential bow of her head. "I will prepare a bath."
"I can't––" Luna stuttered. "That is, I don't––I won't get your sheets dirty. I will rest at the bedside."
Luna didn't even know what she was saying. She was almost delirious. She didn't care where she slept, as long as she slept. Before she knew it, she had collapsed by the door, laying on her side.
She had a sensation of drifting, and instead of a hard carpeted floor, a bed of padded blankets soon held her weight. Celestia's aura vanished, and Luna felt tears well up in her eyes.
"When did you last sleep?" Celestia asked, brows furrowed. Luna met her eyes as she rested her head against the pillow.
"I haven't slept since that night," Luna rasped. "I haven't slept, or ate, or drank...I'm so tired."
Celestia blinked and tears dribbled over her face. Luna finally let her body drift into the realm of sleep.