Luna wasn't herself lately. Anypony that worked at Castle Everfree could see that.
She spent more and more time by herself in her private office than anywhere else, Night Court had been canceled until further notice, and she had dismissed her private guard.
For weeks she had been locked away in her tower office writing decrees and proclamations concerning the governing of the night and changes to the night court.
Starting with the elimination of the old night court council, and founding a new court where Luna herself would be the only pony making final judgment on any case brought to her.
If no pony wanted to see Luna before, then certainly she drove away any pony that worked with her in the past. Her guards, hoof servants, and private council all shooed away from her. Either reassigned to different posts, or given walking papers.
While the entire former night court and staff balked at the idea, only one pony paid no mind.
Celestia slept through the night. Not knowing, or caring what Luna did. When Sharp Tongue approached her, and asked what they were to do with her sister's constantly changing laws over the ruling of night, Celestia only mildly paused before saying, "It is not our business, Luna will rule the night as she sees fit, as We rule over the day."
Daily, Celestia was bombarded with complaints about Luna's changes of staff, either eliminating or shifting positions about to make Luna herself the only pony running the show after dark. The princess of the sun would either give condolence for the lost position, or offer a new one for the day court. But when it came to the one biggest complaint of "DO SOMETHING ABOUT LUNA!" She would just smile and say, "I'm sure that she will be fine, she just is experimenting with new ideas to make Equestria better."
Celestia did not know then, that she would regret her inaction to the end of all time.
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It had been awhile since Nightmare Moon finished her grand palace on the moon. And true to her plan, every day she lay a new brick down on the wall throughout the year, It wasn't a very high wall yet, but it was still getting up there.
All throughout her days, Nightmare muttered to herself in voices, "I'll teach them to lock me away to the moon, yes. I will come back, and when I do they will pay! All those little ponies are going to suffer as I am suffering now! Lets see how they like to be on the moon for two years with no food or water. Lets see how they like their precious sun without an ozone layer to filter out all that radiation. I bet they would BEG for an eternal night at that point."
She walked across the surface of the moon in her never ending search for fallen ice chunks, talking to herself just to hear a voice, "And as for my sister, oh I don't want to even call her that any more, she is no more family to me after this. Oh I'll lock her on the surface of her overpowered star and see what she thinks of its never-ending heat after that! Yes, she will char and burn like a gryphon's barbecue meal."
The sun beat down on Nightmare's black coat as she walked, but did not care. The harshness of the sun on the moon was easily a million times better than the darkness of night on the moon, with no light other than the stars feeble twinkle and no heat at all, practically freezing her solid.
"And furthermore," The fallen princess continued as she marched on, "I will decree that anypony that begs for forgiveness, shall have it! I am not a monster, no matter what that overpowered sister of mine would tell them! No, I will be merciful, even if they don't deserve it... I will forgive anypony that simply asks for it."
Nightmare Moon looked up at the sky at Equestria, and saw the glowing of the biggest cities’ lights, glowing brightly with their fire. "I can be forgiving."
Nothing answered her. The statements hung in the air for nothing to latch onto as Nightmare Moon continued to wander across the lunar landscape.
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A week later Nightmare Moon still was wandering in an eastward direction.
She had grown silent at last as the bitterness grew in her heart. Not to the little ponies, they did not know better. But to her sister Celestia, she would bide her time and on return have her revenge. Even if it took a thousand years to get back home.