"Are you sure that you looked everywhere, sister?" Celestia asked. She and Spike had been covering for Twilight's duties in her absence, so she only ever saw Luna at sundown. After a few days without seeing any sign of Twilight, Luna was tasked with looking through the dream realm to find her. However, it had been 13 days, and Twilight was nowhere in sight.
"I have, but she seems to have just... vanished. Did you tell the others yet?" Luna said,
"I didn't, but I know Spike sent a message to Thorax, Ember, and Cadance. They are starting to worry that a new threat has taken Twilight. Are you sure that you looked everywhere?"
"I am sure, but I will check again tonight. I'm sure that she's safe. Remember, she knows a lot about magic, and I'm sure that she's smart enough to figure things out on her own. If she wants to be found, she'll find us soon." Luna reasoned.
"Do you think she might not want to be found?" Celestia asked, hesitantly.
"Well no, but it is still a possibility." then Luna mumbled, "it's better than some of the other options."
"What'd you say, Luna?" Celestia questioned.
"Nothing, sister."
"Luna," Celestia commanded, trying to make her sister tell her what she had said.
"It's not good for you to worry, and I need to continue my search." Thinking that tonight, Luna may find Twilight, Celestia gave up on questioning her.
"Okay, good luck, I hope that you find her."
"Thank you," Luna watched Celestia walk off to one of the guest suites. Her old room was occupied by Twilight, and if she was going to come back soon, then it wouldn't be right to rearrange it. Once Celestia was gone, Luna gazed out at the stars behind the stained glass window depicting Twilight and her friends battling herself as Nightmare Moon.
If I can't find Twilight soon, then she's either hiding from us, sleeping during the day, in a coma, gone, or worse; dead. Twilight smart though, she wouldn't allow herself to be killed, especially if someone was in danger. I'll find her soon.
Luna broke her gaze from the stars and walked up next to Twilight's throne. Then, she performed a spell to enter the dream realm.
In the dream realm, there were many glowing blue balls, each representing a pony or other creature that was sleeping. The dimmer the ball, the less magic they had. Aside from Celestia, most of the balls were about the same brightness level.
Luna saw that most of the ponies were having good dreams, but a few were having nightmares. Luna was tempted to help those having nightmares, but she knew that she had to keep looking for Twilight.
The dream realm was about half the size of Equestria, so Luna was able to cover the whole planet in a few hours by floating around. She also used an echoing spell to be able to find any trace of Twilight's magic, so she wouldn't have to look at each dream. She found several dreams of ponies she knew, most being Twilight's friends, but none of them responded to her echo spell.
After Luna had covered Equestria's portion of the dream realm, she ventured out into the other kingdoms, including the Crystal Empire, the Changling Kingdom, Seaquestria, Mount Eris, and many other places. Eventually, she had reached the end of the dreamscape. After that, there were presumably no more creatures living out there, since it was outer space. The dream world was flat, unlike their planet, so Luna was able to float out into outer space very easily. Last night when Luna reached this place, she had turned around and given up for the night, but this time she was more desperate, so she cast another echo spell.
Nothing.
Luna tried again, this time using a more powerful version of the spell.
Nothi-wait.
Luna felt a very fain speck of magic echo back to her. It was so faint that she couldn't tell if it was Twilight's magic or that of something else, but she decided to head out to it.
Luna flew very far, checking every so often to make sure that she was heading in the direction of the magic. Eventually, she felt the signal return stronger, but she was getting weaker. The farther away she went from Equestria, the harder it was to keep herself in the dream realm.
I must've traveled at least the distance of Equestria by now. Luna thought. She had spent so much time in the dream realm that the sunrise was now only an hour away. However, she soon saw a blue glowing light off in the distance; it was Twilight's dream. Luna was confused about how Twilight ended up so far away, but she kept going. When she was close, Luna saw several faint glowing blue balls, but she ignored them and went over to Twilights'.
I've found her! Luna thought, excitedly. She looked into the image of Twilight's dream and saw that she was having a nightmare.
. . .
To say that Twilight was overwhelmed was an understatement, Twilight was having a full-on panic attack. The guards from Terram had arrived at Equestria, and it was up to Twilight to fend them off all by herself. Twilight was panting as the guards surrounded her next to the walls of Canterlot. She looked around for an opening in their line as she backed up, feeling a sense of panic rise up in her throat. Then, she hit the outside wall of Canterlot and felt herself suffocating as the guards closed in around her. Then, a bright light occurred, and all of the guards disappeared, replaced by Luna surrounded by a glowing white magic bubble. It was similar to the one that she had seen when fighting the Tantabus.
"Luna?! How'd you get here?! Wait...This is a dream, isn't it!?" Twilight said, relieved that the recent events did not just happen.
"Twilight!" Luna cried, she looked very happy to see her, but there was also a bit of concern in her expression.
"Luna! I've missed you, and Spike, and Starlight, and Celestia, and all of my friends! It has been so hard here without you all! Wait...was everything a dream? It felt like several days!" Twilight said.
"It has been 13 days, actually. The only thing that was a dream was the strange creatures in Canterlot."
Twilight looked a bit sad at this, it felt like a weight had been lifted off her, then put right back on. "Oh, okay then. How come you never contacted me in those 13 days? I know I wasn't mentally there for the first few, but what about last night? Oh no! Were you captured by them as well?! Where's everypony else?!" Twilight bombed Luna with questions.
"I tried to find you," Luna replied, "but you are so far off in the dream realm that I don't think you're even on our planet anymore, that's why I have this bubble around me, as it takes lots of effort to stay here. I don't know what you are talking about with being captured, but I assure you that we are all safe." Luna spoke in a calmer tone than Twilight, but she was worried after hearing a little about what Twilight went through.
"So they're okay? Tell them that I'll get back to Equestria as soon as I can!" Twilight said.
"I will, but I need to leave now, the Sun is rising here, and I can feel my powers weakening. I'm glad that you are okay." Luna said
Twilight looked panicked and sad seeing that Luna was leaving. "Wait! Can't you stay?" she asked, like a filly, "Which direction was I in the dream realm?!"
"Northeast," Luna said, before disappearing in a flash of light.
"Luna!" Twilight yelled, the first familiar face, and familiar creature, that she had seen in days had just disappeared, and Twilight felt her confusion and panic resurface as she woke up screaming.
Twilight calmed herself down enough to stop screaming, and instead, she pulled the covers of her bed over her, and she hid from everything outside. That is until she heard a knock on the door.