Horror.
Not like the effects of the Spell That Must Not Be Named, that was horrifying, this was just the sense of impending doom and the accumulation of feelings of dread and suspicion. There was fear, there was uneasiness, there was Sunset's hoof waving in front of-
"TWILIGHT!!"
"Eh, huh?"
Sunset was giving her a particularly emphatic scowl. "Were you fantasizing about your stupid brother again?" She went on before Twilight could even do her angry-pout thing. "This is serious, we have to keep it together or you know what will happen! Now let's go over the failsafes again."
Moondancer, the only one in the dormroom not flipping her lid, casually flipped to the next page of the magazine she was reading on her bed. "You guys are making a way bigger deal of this than it is. Exams are over for the semester, it's summer time, we should be-"
"We should be prepared," Sunset said sternly, "and this time we will be."
Twilight nodded once, getting her thoughts together. "Sunset's right." She didn't let the little note of surprise that Sunset didn't have a comment for that slow her down. "Supplies are more or less taken care of via what we can store here in the dorm and the hidden stockpile accessible via a specific series of teleportations."
Sunset gave her a small smile. "Good thinking with that one, by the way."
Her rival returned it. "Thanks." She had only thought to keep a week's worth of food and such in the dorm last year, but it still sprung on them when the week was up.
"So," Sunset stated authoritatively, "the doors and windows are all sealed with the level six interference runes, the anchoring spells in the floor, ceiling, and walls will need daily reinforcement as well as the protective redirection matrix wrapped over the vicinity, nopony goes anywhere during the day, and at night we only go two at a time at most if we need to go somewhere so that when they get back, the third can invoke three out of that hour's eight alternating series of phrases and responses to determine that everypony is who they say they are. Failure to do means somepony gets set on fire. Any questions?"
"None here," answered Twilight with a serious face, doing her best to salute like Shining would have in this situation. After a moment, she frowned. "Though I do kind of wish holing up here didn't mean I couldn't go home to see my family for the summer."
Sunset scoffed. "Easy option for you two, maybe!"
Moondancer frowned. "I don't even wanna go home!"
"Nice to see at least one of you sticking with me."
Twilight looked hurt. "Sunset, you're being ridiculous, I don't want it to happen any more than you."
Keeping her eyes on the ground, Sunset still looked considerably agitated, and not because the anchoring spell in the floor didn't mesh with the redirection matrix as well as she would have liked, or because Moondancer's Cloaking Sphere wouldn't really do them much good here. Her mouth twitched. "S-sorry," she whispered, "I just-"
"I know," Twilight gently cut her off, smiling a little, "it's just the stress talking, it's okay. Don't you worry, we'll get through this together!"
As the two locked eyes, silently remembering why they valued one another's friendship, Moondancer nearly squee'd. "You two are so cute together!"
Moment ruined, they turned to her with deadpan stares, speaking in unison. "Ohh, shut up."
Giggling, Moodancer sat up. "So we're totes sure that the whole room is secure? No way anything gets in or out when we don't want it to, everything accounted for, from the windows to the bathroom?"
Sharing a split second of panic, Twilight and Sunset's heads both snapped to the little restroom adjoined to their dormroom. They got up, Moondancer following. Double-checking the constitution of the spells in place on the bathroom floor, Sunset looked up to see Twilight doing the same with the ceiling over the bathtub, likely worried about the effects of condensation interfering somehow. She saw Moondancer standing in the doorway, stretching out like a cat that just woke up.
She seemed to notice Sunset's raised eyebrow. "Yea, yea, I'm coming, I'm coming." She rolled her neck to the left and right. "Think I might'a been laying there too long."
"We should probably close the door," offered Twilight, "it's a little cramped with the three of us in here." Moving so as not to be standing on top of one another, (to Moondancer's slight disappointment) they closed the bathroom door and took stock of the protective enchantments in the smaller chamber.
"Of course," Sunset said under her breath, "the mirror!"
Twilight rolled her eyes. "Please tell me you're not still thinking about fourth-dimension dark spirits or whatever. They're not even a myth, they're complete fiction."
It didn't look like Sunset was joking. "Yea, that's what you say, until another reflective artifact nopony can explain is found. Is it that ponies, and whatever came before us, like enchanting mirrors, or that there's something inherently off about them? Maybe for a good reason?"
"The first one," deadpanned Twilight, "infinite times the first one. Besides, that wouldn't even have anything to do with-"
Not minding Twilight's usual close-mindedness with these things, Sunset rolled her eyes. "Well I'm not taking any chances." She integrated the mirror into the array of spellwork protecting their dormroom.
Stopping to admire her own teeth for a second, Moondancer raised an eyebrow. "So, what about the toilet?" Her two best friends were apparently thrown. "I mean, I don't know how likely it is, but couldn't something slip through the pipes? Immense 'ew' factor notwithstanding?"
They turned to look at it, Twilight smirking at Sunset. "Well? Are you worried about those evil toilet spirits too?"
Sunset blushed a little, then smirked back. "Sorry, I thought that was your area of expertise."
Twilight turned red, glaring at her. "YOU-"
Moondancer went ahead and did for the toilet and sink what Sunset did with the mirror. "Okay, I think that'll do, now let's get out of here before this gets weird."
More or less satisfied, the three walked out of the bathroom, the sand warm under their hooves as-
They collectively stopped, took a quick look around, and found themselves on a beach right next to three towels under umbrellas. Posted to the umbrella was a note.
My Faithful Students;
Congratulations on another successful year! Please, take some time off and enjoy yourselves for a while. There are a variety of places to eat for free at the nearby boardwalk, my treat!
-Princess Celestia
Looking back, the doorway to their dorm bathroom shut and vanished before their eyes, leaving them stranded on the beach as part of an enforced summer vacation. The train back to Canterlot wouldn't be here until much later. Again.
Sunset and Twilight shouted in unison. "EVERY FREAKIN' TIME!!"
Moondancer shrugged. "Well, might as well have some fun now that we're here, right?"
She would have felt bad about being the pony to give the signal to activate the portal in the bathroom door, but Celestia did ask nicely.