After Burst's second victory over Sombra...
Sombra groaned as he regained consciousness, and saw an incredibly angry Nightmare Moon staring him down. "Came to save the hide of your prospective boyfriend?", Sombra said with a smirk. "That'd explain why you took me down before I could charge up a blast."
"When I told you Burst wasn't to be harmed, I meant in ANY way."
"You wanted his heart, and I helped you obtain it. But just know one thing. You're far more cruel than I am. Especially since you stopped me from firing that blast at him."
"What are you talking about?", Nightmare demanded. Sombra let out a dark chuckle.
"Heh heh. None of my business. Go ahead. Have your boyfriend turn into an ice cube or a pale, lifeless shell. That's all that awaits your promised eternal night. A barren world slowly freezing over."
"You...you don't know what you're talking about!"
"Don't I? I'll leave you to your own devices for now. Me? I have a plan to make..." Sombra slithered back into the shadows. Leaving Nightmare alone with her thoughts. Nightmare then pulled out her phone, and pulled up a contact.
"Sunset? It's Nightmare. You know I wasn't involved with what happened today. It's just, there's something I want to know. Meet me at the school. Thank you." Nightmare turned into mist, and floated over to CHS where she returned to her regular form. Sunset soon arrived. "Thanks for coming."
"Just what did you want to know Nightmare?", Sunset asked.
"Sunset? What would've happened if I brought eternal night back in Equestria?"
Sunset sighed. "You really didn't think things through did you? If you had defeated Celestia a thousand years ago, everything would've changed slowly. Without the light from the sun, no plants would grow. That would mean a whole lot less food would be available. And with no heat from the sun, the planet would gradually grow colder and colder. Soon, all of Equestria would be a giant ice ball. And...a lot of ponies, or in this world's case, people, would die from starving or cold. And it'd be painfully slow." Sunset then noticed Nightmare's pained expression.
"Sombra was right.", Nightmare barely whispered as she came to a realization. "She knew. Celestia knew that would happen! That's why....!" And then it hit her full-force. "That's why she used The Elements on me and Luna! Why we were stuck on the moon for a thousand years! Why Luna..." The realization of just how much harm she had caused. "Why Luna was so hurt and alone all that time. Why she wouldn't talk to me for all those years...I hurt her.....When all I wanted to do was.....I need to go!" As Nightmare left, Sunset texted the others. She told them everything she knew, and about all the events that had transpired.
"Nightmare. Just what did you want to do for Luna?", Sunset thought out loud before meeting with the others. When they arrived, they were a mix of surprise and anger. Sunset told them the full story. "And that's her story up until now."
"And you're saying...this is the SAME girl we welcomed just yesterday? The same one staying with Burst?", Inferno asked.
"The same one who brought Sombra back?", Applejack asked.
"The one who was the reason Princess Luna was imprisoned on the moon back in Equestria?", Rarity asked. Sunset nodded.
"Isn't she also the one who tried to make it be night forever?", Rainbow Dash added.
"Yeah. All of those and more. Gold and I knew who she was, but we didn't want to risk causing a panic. She hadn't done anything drastic. Even if she was the one who revived Sombra, she regretted what he did to Burst. But...something changed her. Now, I don't think she has the same plans for this world. Especially after I told her what would happen if she had brought it. Sombra actually played some part in it. But most of all, I think Burst is the one who started her change. She picked up on his power in specific back in Equestria, and followed it here. Burst made her feel welcome, he introduced her to us, and he showed her things she's never known before. I never thought someone like her could ever change. But I did. So did the Dazzlings. And now that you all know this, here's the big question. What do you think of her now?" The group shared uneasy glances before each one gave their response.
"Well....I guess she's still pretty cool.", Inferno answered. "You said she regrets causing Burst's break-up, and she's not acting like the one you knew."
"Man...he's right. I mean, we only know the Nightmare Moon we've met.", Steel noted.
"Maybe, we should give her a chance.", Ace said.
"We were banished from Equestria, but we had each other.", Adagio said as she looked at her sisters. "But, Nightmare has no one." Veenus and Fang nodded in agreement.
"She didn't seem so scary...", Fluttershy added.
"She enjoyed the party we threw her!", Pinkie chirped! "You're only REALLY evil if you hate parties!"
"Ah don't think its fair ta judge her just because of her past.", Applejack said.
"Aj's got a point!", Rainbow Dash added. "It'd be pretty lame if we just started hating her because of what's already been done!"
"Indeed darling.", Rarity chimed in. "It wouldn't proper of us to do that to Nightmare after we just got to see a side of her no one knew about."
"Then I guess...all that leaves is Burst.", Sunset said. "But the only question is, how's Burst going to take it? And who's he going to choose in the end."
Meanwhile at Burst's house...
Nightmare had just arrived at Burst's house and went inside. Lumina greeted her. "Hello Nightshade. Did things go well today?"
"Things were....interesting. I just need to think about things.", Nightmare replied as she went to her room. Once she closed the door, Nightmare wept. Her mind drifting back to Luna and their banishment. 'Luna....I'm so sorry!'