The Princess of the Night walked slowly down one of the many hallways in the castle, occasionally passing by one of her Bat-Pony guards who would give a quick “hello” or simply nod their head. Though Luna barely noticed. With her head held low she made her way to the lunch room. Upon her arrival she finds herself a seat and is soon greeted by the castle chef.
“Evening Princess. What can I get you this fine evening?” He asked.
“What is wrong with my night?!” Luna asked with panic in her voice.
“Uh, come again?” The chef asks slightly puzzled.
Luna narrows her eyes dangerously at him.
“I did not stutter. What. Is. Wrong. With. My. Night?” She asked again.
“What do you mean Princess?”
“Why do the ponies feel that they must sleep during the night rather than the day? You and all my bat pony guards sleep during day, do you not?”
“Well, yes. But the ponies of Equestria–”
“Are insulting! All my hard work that I put into creating the night is for nothing if they choose to not enjoy it's beauty! Surely you agree with me, yes?”
“W-Well, not exactly...ponies aren't like us, you see. They need sleep during the night as a way to be fueled for the day.”
“LIES! If you and I do not require sleep during night hours, they are no exception!!”
“But Princess–”
“GET OUT OF MY SIGHT!!!”
“But–”
“Unless you wish to lose your job you shall leave me this second!!!”
“Yes your highness! My apologies!”
The chef quickly makes himself scarce and leaves. Luna remains seated for a few moments before she too gets up and begins to stroll down the hallway. For a few minutes she is silent. The only sounds to be heard are the ‘clip-clop’ of her hooves against the floor. Head hung low, Luna bites back her anger temporarily as she treks down the long hallway.
Finally, Luna brings her head up and looks at the world through a large window. She takes a deep breath and begins a harmonious melody.
“Now the hour has come at last, the soft and fading light. Has crossed the west horizon, and bidden us goodnight. And what a lovely night it is, to walk a moonlit field.”
Luna continued looking out the window as Celestias' sun set for the night.
“To see the softer shades thar are by starlight now revealed. So why it is that now, when all is quiet and at rest. When candles glow and all the world is at its very best.”
Luna walked down the corridor, unaware that the castles own Mage, Starswirl the Bearded was watching her from the ground level.
“The ponies of Equestria, should lock themselves away? To shun the moon and wait instead for sister's sunny day!”
(In umbra Luna est)
As the song picked up, the transformation began. As the transformation grew, so did Lunas' hatred and anger. Lunas' pupils went from normal to little slits.
“Am I so wrong to wish that they could see things like I do?! And am I so wrong to think that they might love me too?!”
Images of ponies appeared in front of Luna and began bowing to her. The images soon disappeared as quickly as they appeared. The scene changes to an image of a group of ponies bowing in front of a larger image of Celestia.
“Why shouldn't they adore me? Is it not within my right?”
In a fit of anger, Luna flared her wings and stomped her front hooves on the ground as the doors behind her swung wide open, causing the images to blow away in the wind. Much like the images, the anger in Luna's eyes disappeared only to be quickly replaced by a look of determination as she stared out into the sky.
“I'll not be overshadowed! Mine is not the lesser light! I've waited long enough now! For them all to come around! And though the Sun may plead and threaten! The Moon will stand her ground!”
Luna's horn glowed a light blue before firing a bolt of energy into the sky. The energy traveled up and up, until it finally hit the moon and transformed the whole sky from dark night blue, to blood red. The scene panned outward to show Princess Celestia fast asleep in her room.
“It has come to this at last, I will no longer yield the sky. If they cannot love but one princess alone!”
Starswirl watched Luna from behind a wall. The Princess of the Night smiled with a crazed look in her eyes as she bellowed her song into the night sky.
“See, the moon is rising! She has come to claim the heavens for her own! And all will know the wonders! Of my dark and jeweled sky!! When all the world is wrapped in an eternal lullaby! SO SAY GOODNIGHT!! To this, the final setting of the Sun!! Tomorrow dawns in darkness,
The Night, Time has BEGUN!!!”
(Nocte)
As the song drew closer to the end, Luna's voice began to change, becoming deeper and higher in pitch. The final part of the transformation happened as Luna's fur turned from deep blue to pitch black, her teeth grew sharp and razor like, she grew in height, and her large feathered wings lost their feathers and were replaced by wings that were not unlike a bat. Watching this, Starswirl the Bearded turned around and ran into the library while Nightmare Moon bellowed with laughter.
“Ha ha ha ha ha ha!! HA HA HA HA HA HA HA HA HA HA!!!!”
Meanwhile Starswirl made his way through the library and approached Celestias' bedroom and was met by two guards.
“State your business Wizard!”
“I must see Celestia immediately! It concerns her sister! Please!”
“We will let her know you request her attention.”
The guards turned and enter Celestias' room before waking her from her sleep.
“Your Highness? Starswirl wishes to speak with you.”
Celestia awoke and spoke half annoyed and half groggy.
“What is it? Can it not wait until tomorrow?”
“Not according to him your Highness. He says it concerns Princess Luna.”
Celestias' eyes widened in surprise and fear before she spoke.
“Tell him I'll be with him in a moment.”
Both guards bowed low to the Princess.
“At once your Highness.” One of them says before they both walk out of the room.
“She'll be with you in a moment.”
“Thank you.”
After a few more seconds, Princess Celestia opened the door to her room before beckoning the old wizard inside.
Starswirl walked inside and saw Celestia looking at him with an expressionless face.
“I'm told you have information on my sister?”
“Yes your Highness.”
“What is it? Is she okay?”
“She is unharmed. However, I don't think she's the same Luna you know and love. She's...different. Not herself. I watched her transform before my eyes. She's more like a demon now. Almost as if something has possessed her and is now controlling her body.”
“Where is she now?”
“In the throne room I believe.”
“You stay here and alert the guards in case I do not return. I know not what has happened to my dear sister, but it is not her you have seen. It is something else. I'll see to it that this monster is dealt with.”
“How will you do that your majesty?”
“Whatever I have to do. No matter the cost.”