"Guard? Guard!" Luna yells at the incompetent stallion outside her sisters chamber doors. This is the third time she had caught this one Stallion dozing off.
The hallway they where in is a beautiful hallway. One of the most beautiful, as to bring Celestia to a good mood in the morning. It has magnificent, shined, pearl white Marble floors. Pillars on the walls every few hundred feet, and the wall parallel to Celestia's door was nothing but a giant window. Celestia requested it herself so that she can open her door to a beautiful sunrise.
"Stay awake guard! This is my best work!" She tells him, gesturing towards the window wall with her hoof. The guard looks out the window to see a full moon, and a couple clouds going over the moon. The sky cast a breath taking purple.
"I-it surely is a sight to see, y-your highness." He says with a yawn.
"Yes, it is." She replies with a nod. After reminding the guard of the dangers of slacking off, she was on her way.
Walking along the marble floors with her hooves echoing, she hums happily to herself. And that happiness stayed for as long as she was in that hallway. For as soon as she walked into the throne room, she saw the two guards who are supposed to be awake and next to the throne, asleep, on the throne.
She walks up to them and uses a voice, just under her Royal Canterlot voice.
"Guards! I was not aware that it was your break time!" She shouts, scaring them awake. They shoot to attention with fearful look in their eyes.
"Are you unaware of the dangers of slacking off?" She asks them, lowering her voice a bit.
"N-no your highness." the one on the left replies.
"We apologize deeply, your highness!" The one on the right says, bowing. And once the one on the left sees this, he bows as well.
"Yes, yes. If it was not for the lack of staff, I would surely get rid of you two!" Luna states. Then turns around and walks away. Hopefully to go do get job, instead of reminding others to do theirs.
Princess Celestia and princess Luna sit at their breakfast table. Eating the pancakes Celestia made.
"Hey, Tia." Luna finally breaks the silence.
"Yes, lulu?" Celestia responds with a smirk.
"Do not call me such a childish name, sister." Luna demands.
"You are my baby sister, so you will have a childish name." Celestia replies, giving Luna a smile. Due to that conversation, Luna forgot her train of thought. They sat in silence for a little longer until Luna remembered what she was going to say.
"Hey, Celestia." Luna says, her gaze shooting daggers. "Can you do something about the night guards? The continue to fall asleep, and I need to continually wake them up. Do you have some kind of spell or something?" Luna asks, but didn't get a response right away.
"No." She says a bit later. "No, I do not have a spell to make the guards stay awake."
"All right, sister. Do you know of anything that would make them stay up?" Luna pushes. Celestia thinks for a bit. Then responds a bit later.
"I know of one thing. But-"
"Tell me!" Luna yells, but then remembers to say "please?"
"Buuuuuut." Celestia continues. "I will not tell you. For it is forbidden, but if you most know, it it's in the book of transformations. In the library. Look if you're so curious. But I warn you, sister. Do not try it in the daytime." She says.
"Yes sister!" Luna says exidedly, then finishing her breakfast.
"Slow down!" Celestia tells her "don't want to choke now."
"I am finished! Sister, I will now go 'hit the hay'" Luna says with a laugh.
When Luna woke up, she hopped out of bed. She had to get to the library and find that book! She opened her chamber doors, startling the guard outside it. He stood to attention as she walked out it. As soon as she was out of that guard's line of sight, she began trotting towards the library. But as she kept trotting, she couldn't remember where the library was. As soon as she spotted another guard, she went over to him.
"You! Mr..... What is your name?" She asks him.
"My name is quick strike, your highness." He says.
"Mr. Strike. Where is the library?" She asks him.
"It is-"
"I think it be better if you show me, I'd forget quite quickly." She lies. He nods and walks back towards where Luna came from. Following him, Luna began thinking up reasons to make him stay with her, hopefully so she can use the spell she is too find, on him.
"Princess?" Strike asks.
"Yes, Mr. Strike?" Luna responds as they round a corner.
"Just for the sake of conversation, and if you allow it. May I ask why you need the library?" He inquires, hoping not to get an earful.
"You may. I need the library to confirm something sister had told me. I want to make sure it's not a joke she's pulling over me." Luna responds.
"Alright." Strike says.
They walked in silence for the rest of the walk. They made it just before Luna went mad.
"Here it is, your highness. If you need me. I'll be right here." He says, standing to attention next to the library doors.
'perfect' Luna thought 'he's not going away.'
"Thank you, Mr. Strike." She says. The guard gives Luna a bow as she walk into the library. Looking around, she curses under her breath. Hoping it won't take forever to find the cursed book.
"Aha!" Luna shouts. Pulling the 'Book Of Transformations' of the shelf with her magic. Flying down from the tenth shelf, she sets the book on a table. Pulling over a cushion, she sits down and opens the book. It took her another half hour before she finally found what she was looking for.
"This might work! Bat-ponies!" She says to herself exidedly. " 'These ponies are known for their loyalty, and their nocturnal capabilities.' " she reads. Then reads the creation methods.
" 'there are two ways to create a bat pony. The first way it's too cast a spell, which affects last for half the lunar cycle. Second method, is to take a young foal, and with every meal, feed them two drops of bat blood for a full lunar cycle.' " she reads a loud to herself. Cringing at the thought of feeding bat blood to Young foals.
"Guard!" Luna yells. A couple seconds later the library doors open and in walls strike.
"Yes? Princess?" He responds.
"Come here." She motions. He complies.
"Stay there." She tells him, then looks at the book. Reading the spell in her head then turning to the guard. Her horn lights up a dark purple, than it shoots a purple beam at the guard. Engulfing strike in a purple and black or, was Luna's magic. Then in a bright flash, it was over. Standing where silver once was, it's a dark coated, creature. Having wings of a, well, bat. And fangs of one too.
"Yes." She says to herself. "This will do quite nicely."
Author's Note
This is the first, third person pov story I've written, so it's a bit different for me. But hopefully it turned out well. 
Author's Note
Okay, so I had no idea on how to write in Luna turning into nightmare Moon, so I split the story into two chapters. Second one where she is nightmare Moon.
Nightmare's new family
"guards!" Nightmare moon yells at the Bat-ponies in the throne room. They come over to her and bow at the foot of the throne.
"Yes? Your highness?" They said in unison.
"What is it you need?" The middle of the five asked.
"I need you to go about my kingdom, and take every little foal and filly from their home and bring them here, to my throne room. Take them no matter the cost." She demanded. The one in the middle stood up, but the other four stayed down.
"Princess? If I may?" He asked.
"Speak!" She shouts.
"How far would you like us to go?" He asks.
"Take every guard in the palace! And go to every city, every town, and every village that is inhabited by ponies, and grab every foal and filly you see!" She yells. And with a nod, he, as well as the other four Bat-ponies, were off.
"In here!" A guard yells, busting down the door of a townhouse. "By demand of our princess, Nightmare Moon, you are to hand over your children!" He yells at the mare on the other side of the room, a foal and a younger filly behind her.
"Your not getting my children!" She shouts, sending a blast of magic towards the guards. Dodging the blast of magic, one of the two guards in the room lunges forward, sinking his spear deep into the chest of the mother. Collapsing emediatly, the mare drew her last breath. Pulling his spear out of the corpse and wiping the blood off on it, the little filly and foal watch, mortified. Pushing the dead mare out of the way, the second Bat-pony grabs the children. With little struggle, he picks them up and carries them out on his back. Walking up to the cattle carriage and opening the doors, he tosses them in, then looks at the dozen other foals and filly's he's gathered. Knowing he's doing this for his mother of the night, he closes the carriage, feeling no regret.
"Yes, yes!" Nightmare Moon cackles. Looking at the dozens and dozens of little foals and filly's crowding her throne room.
"What are we going here?" A filly in a corner pipes up.
"Who said that!?!" Nightmare bellows. Emediatly one of the guards points towards the filly who did. Nightmare hops down from her throne and walks over to the filly. Walking over, she notices a foal cowering behind the filly. As she walks up, she stretches out her wings and keeps them extended. Both for dramatic effect and to strike fear into the two children.
"It is none of your business why you are here!" She bellows again, getting closer and closer. All the while, the two sink deeper and deeper into the corner.
"It is not your concern why you are here! You should be honored to be in the presence of such a wonderful and magnificent princess!" She continues, her wings still extended.
After a full minute if just standing there, she contracts her wings and walks back to the throne. Nodding to the guards, the begin to hand out bowls of oats. And only to nightmare's knowledge, they contain two drops of bats blood.
"Now children!" She yells. "Welcome to the FAMILY!"
