Some policeponies charge the alicorn, but she just laughs and takes off out the window into the dark.
Clarity forces herself not to break into a canter that will guarantee her a timewasting trip over her own hooves as she makes for the exit. She doesn't know any part of Ponyville well enough to teleport there without looking straight at it in better light than that of the stars and the suddenly blank-faced moon, so on hoof it'll have to be. She doesn't know for sure if the contents of her saddlebags are going to be useful in the Everfree Forest - actually, she'd put her bits on 'no' - but while this is an emergency, it is not an emergency on a scale of minutes and so she's going to go ahead and take the precaution.
"What do you know about this that I don't?" inquires Cordy.
"Nightmare Moon equals Mare in the Moon equals banished sister of Celestia, could theoretically be defeated with five mysterious and one extra mysterious objects that can maybe be found in an old castle in the Everfree Forest," Clarity recites, not breaking stride.
"And you mean to go get them? Sounds reasonable. I'll help plan the expedition," says Cordy. "We should bring Guiding Star and Silver Streak for informational purposes, and Brightblaze would be good to have along in case of trouble, plus there's no way she'll stay behind if her sister is going."
"I... was not expecting to have company, but if you're any good with large predatory animals on top of little singing birds I'd be glad to have you, and Guiding Star makes sense too, explain the others?"
"You saw Streak's cutie mark? She answers questions," says Cordy. "Solves mysteries. Finds out facts. If we find the Elements of Harmony and can't figure out what to do with them when we get there, it's a good bet she'll be able to offer some insight. And I'm sure you've seen Blaze fly, when she cleared the sky; those boots of hers will be good to have around if it comes down to a fight of some kind. As for large predatory animals - I did say I can communicate with anything."
"Okay, you can all come if you want, but - at your own risk. I feel bad enough that I didn't successfully get Celestia's attention with my warning; I'm sure you all know, living right here, more about the forest than I do, but still." Here's the library; Clarity opens it up and collects her saddlebags.
"Believe me, I'm aware of the risks." She cocks an ear at the sky and adds, "Oh good, Streak must have heard us."
Guiding gallops up presently too. "Why are we all going to the Everfree Forest with Joy?" she demands.
"We're going to find some mysterious objects Clarity read about that she thinks might help defeat the scary night pony," says Cordy.
"Okay, but Joy'd better behave himself or I'm not going to be that much help tracking them down - I wonder where he is."
"Well, he wasn't on the shortlist for invitations, so if we just head for the forest now he'll probably find us on the way, won't he?" reasons Clarity, and she starts off.
"Hey, Blaze, hey, everypony!" he says. "Where are you all headed?"
"We're going to the Everfree Forest to find artifacts that may or may not still be there, may or may not prove usable, and may or may not help, and apparently you're joining us."
"Guiding, you want to take a moment to make sure we're all intact in a while?"
Guiding stops, casts her spell, and presently reports: "I see us all in the forest with all our limbs and everything. Joy, behave, okay?"