Apple Crunch couldn't sleep.
There hadn't been anything to do last night, no Nightmare sightings, no "Mutagen" (the Turtles explained that), just boredom in the sewers. Plus, he was going to have another cousin! He loved family- even more then work. So he was the first one to hear the Foot. His ears pricked as they detected repeative marching and robotic squeaking sounds.
"Guys, wake up!" he shouted, "Someone's coming!"
Everyone was immediately awake, jumping up ad looking all around.
"I don't see anyone, Crunch..." Thunder sounded unsure.
"Don't look!" Harmony realized what Crunch meant, "Listen! ...Oh... I mean, if you want to sleep, you-you can..."
Although shyness crept into Harmony's voice once again, that didn't stop anyone from listening.
"Yeah... yeah, I hear it, too," Calamity nodded seriously (although she was still, of course, smiling).
No one argued as Thunder Bright lead them out of 'the Lair'. Although, no one else came besides the Elements of Harmony.
"Alright- We've noticed that the Turtles and Mrs. Rarity-" (Dawn said the name with utter disgust) "-have stayed in their Lair. So, you should go with the Foot, and I'll scout out the others by myself," the Alicorn explained.
Tigerclaw nodded, then turned to say something to his second command, Rahzar. The mutant dog nodded and ran down to tell the Foot. After a minute, there was a straight line dividing two groups of the Clan.
"See you.. later," Tigerclaw forced a twisted imitation of a smile with his killer-sharp teeth. Dawn nodded. Before the Alicorn went down to search, however, her horn glowed grey once again and she was bestowed an almost-perfect copy of Nightmare Moon's old armor- but this one was midnight black with an attachment that covered her mouth as well.
After seemingly hours of searching, Dawn finally found the Elements of Harmony. They were looking for someone, but they didn't know it was her. She jumped down suddenly with the element of surprise, pinning Calamity to the floor with one hoof on her tail and the other on her muzzle.
"HRRMPH!" Calamity shrieked (or tried to).
The others turned to see who their attacker was.
"Hello there, kind ponies," she smiled evilly.
"Let our friend go!" Cloud growled, charging towards the Alicorn. Dawn shot a few grey beams of magic at her, but the Pegusas simply dodged them.
"A fast one, eh?" the Nightmare said to Dawn, "Try something different."
Dawn obeyed, picking up Cloud with her magic an throwing her against the wall.
"Are you okay?" Harmony asked, galloping over to her.
"Yeah," Cloud nodded, "I'm fine."
The two trotted back to the main group of friends.
"Try to get her back," the Alicorn taunted, "I dare you."
"Enough!" Thunder screamed, teleporting Calamity to his side and causing Nightmare Dawn to fall over un-gracefully. She quickly regained her balance, however.
"Who are you!?" Crunch shouted.
"I am Nightmare Dawn! And I have a secret to tell you," she replied. Suddenly, the scarlet Earth Pony was sitting next to Dawn. She whispered something to him, in-audible to the others, and he just stared at her, mystified, before being teleported back.
"What did she say, Crunch?" Harmony was filled with concern.
Crunch said something very quietly that no one else could hear.
"Hmm? I didn't get that," Calamity said, leaning her serpent-like body over. Her nose was bleeding and she had a cut on her side from Dawn's armor, but she seemed fine.
"She said... she said Thunder is her brother," he croaked. Everyone stared at him for a moment, then turned their eyes to the white Alicorn. Harmony flew up to him to look more into his eyes.
"Thunder?" he pleaded, "Tell me it isn't true..."
"It is." Thunder replied, looking away. Although he had no evidence, it was a gut feeling. This was his sister, and she had been possessed by the Nightmare. "But we're going to save her."