The Swish of the Scythe

Three of the four girls were agast. Fluttershy screamed a long, high pitched squeal that lasted for an five seconds but felt longer.
"Ah must say, Ah had a feeling that this would happen," Applejack told Sunset and Pinkie. "And Ah ain't scared in the slightest because Ah know that you want to help Twilight. Ah can tell that you ain't lying. Ah think that it's the magic or whatever it's called, and Ah'm glad to have it. Ah ain't scared of a little blood, even if it means that I have to fight my instincts and lie."
"Good to know, Applejack," Sunset replied, breaking the silence. "To be honest, I really didn't expect the rest of you to react this way. Pinkie was really calm about it. She said that it was fine because she wanted to help Twilight."

Pinkie pulled a trolley into the girls' vision. The sight was unnerving: a glint of metal could be seen next to a glass vial. Fluttershy was scared the most by this. She disagreed with the harming or neglect of all animals and people.
"I don't want to do this," she whispered.
"Fluttershy, shh," Sunset told the scared girl as she approached her, blade and vial in hand, "I am going to do you first. I have enchanted this knife so that it doesn't hurt as much, and it heals really quickly. You can look away if you want. Just remember, this is for Twilight."

"Wait!" shouted Rainbow Dash from her booth. Sunset paused to hear what the girl had to say. "Midnight and Twilight are the same person right now. It's possible that it won't work until Midnight is separated from Twilight. Why take that risk of being found out?"
Sunset told her calmly, "This has been done before, albeit by more powerful supernaturals than I. However, a dash of confidence - and not loads, because that's arrogance just a dash - never hurts. I have just enough faith in my abilities. Plus, although you are untrained supernaturals, I know that you can and will work with me."
"Okay, you can continue."
Fluttershy looked away, felt Sunset turn her hand and take a small bead of blood from her index finger to place in the vial. She untied the restraints, released Fluttershy and moved to Rainbow's booth. She put on a brave face and Sunset took the bead of blood, then let her friend leave the booth. Applejack was completely unfazed and even smiled as she watched Sunset. She had always believed in magic and now knew that her beliefs were true. Rarity was not comfortable in the slightest, but said, "This is for you, Twilight," and did not struggle when she saw the knife. Lastly, she took Pinkie's blood and then took her own. She placed the knife back on the trolley, then asked the girls to make a ring.

Before she joined the circle, Sunset told them, "We don't have long until moonrise, so we need to make this quick. I need all of you to say, when I step into the circle, "I promise never to divulge to the entity known as Midnight Sparkle, regardless of whether she is with her host Twilight Sparkle, that I am a supernatural working to destroy her and prevent her from hurting others." It's not the easiest sentence in the world, but it's enough to make sure that she can't get anything out of us. We'll say it as soon as I'm a part of the circle."
The girls nodded. Sunset counted to three in her head and stepped in between Rarity and the now calm Fluttershy.
"I promise," they all said, "never to divulge to the entity known as Midnight Sparkle, regardless of whether she is with her host Twilight Sparkle, that I am a supernatural working to destroy her and prevent her from hurting others."

A magical stream of light spread from their hands. Each stream connected, then all of the light flowed into the glass vial in Sunset's hands, forming a stopper. When Sunset tried to pull it off, it stayed. She placed the bottle on the floor, and jumped on it. Miraculously, it didn't break. The other girls stared, but Sunset acted as though it was perfectly normal.
"Blood pacts cannot be broken unless everyone who made the pact wishes to break it," she told them. "Now we are a lot safer than we were twenty minutes ago."

They travelled back to Pinkie's flat using magic, and Pinkie sent everyone home. Sunset used magic to travel to her bungalow. She undressed, put on her pajamas and snuggled under the covers. It was likely that Midnight would come to check on her every night. Demons were unable to tell if someone was supernatural or not unless the person revealed their powers. Only Sunset and Twilight's friends knew about their gifts, so they were safe.

Twilight was beginning to transform into Midnight when she had a sudden thought. Why? Why did she allow this to happen? So she fought, and then she heard the demon.
"Midnight Sparkle."
"How can I help you?"
"Do not fight. Become your true self."
"This is not my true self," she said after struggling with herself.
"You wish to see your family again, I know you do. Follow my instructions or you will never see them again."

Twilight allowed herself to become Midnight. This was why she killed without mercy and did not ask questions. She wanted to see her family. Yet, she knew that the demon would never let that happen. He was taunting her, forcing her to kill and controlling her like a puppet. Midnight knew that she deserved it, but Twilight knew that she deserved better, and that she would have to continue with this internal struggle until somebody managed to free her from her misery. Midnight killed two people very early that night, in order to visit Sunset Shimmer. Midnight did not want to die, she wanted to continue doing this. Twilight just wanted to have a normal life and fall asleep and not wake up one day. With any luck, Sunset would be the one to bring her some hope.