Melo revealed a secret piece of information.
"The Holy Sword Church's library as well, if the headquarters is invaded and falls, it will immediately trigger a transfer mechanism; the internal collection will be instantly teleported to another hidden location, leaving nothing behind in the original place."
Naisa also clarified to Reiger the Holy Sword Church's approach, which undoubtedly left more room for maneuver compared to the Empire.
There's no help for it, the former is a nation; once the palace falls, it means the nation is about to be destroyed, so it's better to destroy the royal library, as there are bound to be many unspeakable national secrets inside.
The latter doesn't need to go that far; even if there are any secrets, it won't involve the nation, the race, or even the entire Source, at most it concerns its own rise and fall, so compared to direct destruction, it's obviously better to transfer.
Different standpoint, different status, naturally different approaches.
