"What about the portals?"
Twilight raised her head from the scroll she was writing on. "What?"
"The portals," Celestia repeated. "The ones to Sunset's world. There's one in the Empire too, isn't there?"
"And we could use it as a way to escape if for some reason we decide to." Twilight returned to her scroll. "I've already laid out plans for having that one guarded on the other side. Nothing Nightmare Moon could send through would come out as a problem for what I'll have waiting there, if she ends up finding it."
"But you're keeping Sunset in the dark about what's going to happen, aren't you?" Celestia asked, walking closer as she paced around the room.
"I am," Twilight said. "I've already set up an automatic message to inform her of everything, if I end up unable to tell her about it myself after the fact. I wish I'd found a way to close the portals or even just find them all, but I don't exactly have time to focus on that right now."
Celestia had a muffled, close-mouthed chuckle as she eyed what Twilight was working on. "You're convinced that can work, aren't you?"
"I wouldn't spend so much effort working on something if I didn't think it was possible, not when time is limited and the situation as serious as it is now." Twilight paused and looked over what she'd written again, then continued on. "Hope is a great thing, but it's a dangerous one when it's not bound by some level of realism."
"And you consider applying knowledge you only recently acquired to create a new spell you've never had a chance to test and then using it on a scale this massive as your first attempt at it and only remaining chance to solve the issue to be realism?" Celestia chuckled as she leaned in closer. "Quite brave of you."
"You've raised the Sun every morning and the Moon every evening for a thousand years, when before you just one day of it was enough to leave multiple unicorns drained. You should know that scale is no issue." Twilight pulled out a different piece of parchment with something else written on it, and compared it to what she was working on. "And I did test it. Besides, you'd be surprised by how much has already been written about the theoretical possibilities of transdimensional impositions."
"Resourceful as always." Celestia looked away, and continued to pace until she reached the wall. She stood there in silence for a few moments. Then she continued, in a different tone, "You remind me of myself."
The quiet scribbling of Twilight's quill stopped abruptly, and didn't pick back up until a few seconds later. "It should be no surprise," said Twilight. "I was your student, after all."
"Hmm. If student is the word we're choosing to use."
"It's what Equestria will hear. We may as well."
"There it is." Celestia sighed. She began to walk again, back towards Twilight. "Do you believe me when I say I'm sorry for what I did?"
"If I did not believe you were, you would not be standing here to tell me about it," Twilight said. "For what it's worth, I hope we'll be able to have this conversation again, after this is all over."