Twilight quietly followed behind the mare as she walked down the corridors of the building. At one point, she took a turn, and entered down another corridor with a lower ceiling. Comparing her maps of the place for a moment, Twilight could tell they were moving into an different building, though she had no records of the archive being there. She had no real indication of an archive being anywhere though, so it was probably just a matter of what she had lacking accurate information.
While she walked, she held both of the communication scrolls in her magic and wrote to both Celestia and the unicorns at the laboratory in Nightmare Moon's castle, informing them of her findings. They had approximately three days to prepare, and now they knew the Empire seemed to be the first target. She'd have the citizens taken to safety and anyone who might be particularly helpful asked to be there to defend it. As much as she didn't like the idea of fighting against an invasion, not trying to stop it there would have just made things worse.
She had plans for how to deal with Nightmare Moon. Things she'd been thinking through on her way there. Using the Elements was still the go to option, but if that failed she had come up with an alternative plan. On top of that, she'd already figured out and discussed some more precautions she could take in preparation for the fight.
The mare in front of her reached a door, and stopped, and so did Twilight a little farther back. It was different both from the main entrance and the regular doors she'd seen that far. No apparent mechanism to open it, but it was clearly made up of two separate halves split down the middle. Dark grey, with a blueish square at the centre, half on each half of the door.
Suddenly a slit in the wall above the door lit up, and cast a stream of blue light over the mare like a blanket. It scanned her back and forth, the blue line running over her coat, and after a couple of seconds the square in the middle of the door lit up and the two halves slid one to each side. Twilight was quick to fly in behind her, before the door closed again.
The room inside was large. Wide and tall, Twilight figured it took up the whole building they were in. And yet as large as it was, most of it was occupied by a single thing, if an incredibly complex one. A short distance from the entrance was a glass panel, going from one wall to the other and from the floor to the ceiling, and behind it stacks upon stacks of grey stone tablets, with glowing blue inscriptions, floating in the air and connected to each other by strands of ethereal blue light. The only other visible thing, the only break in the massive glass wall, was a black screen jutting out of it with a series of larger and brighter strands of energy visibly tied to it on the other side, and a metallic keyboard in front of it.