As Astaroth and his friends were dragged to a secluded room in the back of the building, they slowly stopped hearing the cacophony from the front part of the building.
The sudden silence was a welcomed development, but also brought some questions to the group. They weren't that far from the busy part, and already the noise was gone.
Astaroth had already found the answers to this, since he had activated his Perfect Mana Sense when the sound disappeared, and found traces of mana inlaid into the walls.
As they kept walking toward the room they were promised, he inspected the walls. He could see lines of mana following the bricks, imbued with some kind of lettering.
He guessed there was a formation to block out unwanted eavesdropping. As a bonus, the formation absorbed the stray noise from the busy front desks.
There were so many applications to magic that he needed to learn. Every day he stumbled upon new uses he wouldn't have thought of on his own.
