A washroom?
Husen's mouth twitched. He turned to Kallen. "What did you design that for?"
Actually, designing it hadn't taken much effort. The castle's exterior design and such had only required some effort in simulation, and the cost wasn't particularly high.
At least, it was much simpler than Mars's initial suggestion of carving formations directly onto the outer walls. Formations weren't simply a matter of "carving." Just as piling cement into the shape of a formation couldn't activate its effects, a formation was a project whose intricacies lay within, in places unseen.
But before Kallen could explain, Mavario spoke.
"The [Black Prison Castle] is generally used in emergencies, especially for them, since they're about to enter the Gate of Reincarnation for the Trial. Their main objective is exploration rather than attack, so they'll most likely use the castle when they're under attack or a teammate is injured.
"Having an extra washroom inside the castle will provide an effective place to accommodate an injured teammate and better treat his wounds."
Kallen immediately said, "That's right, Instructor. That was exactly what I had in mind."
Husen blinked and coughed. "Oh, so that's why."
"This castle is quite good," Mavario praised. "Have you studied architecture before?"
Actually, that spell-imprinting scroll had included "architectural plans," but expecting a layman to build a house after one look at the plans was far too dismissive of professionals.
However, Kallen had the [Key of the Magic Cube] to run simulations. It was equivalent to rendering the structure in three dimensions in his mind while building it, using extensive calculations to make the actual work easier.
"Instructor, I designed and built a residence myself before."
"Oh, a manor? I'd really like to see it."
"It was a funeral society."
"All right, then it must have had even more