“The Ascension Empire's control was just that much weaker. Maybe they themselves knew this as well, or why else would they allow so many to die…? Maybe they wanted a more manageable population…”
BINGO!
At that time the Spanish we know was not spoken, but a mixture of Latin and Spanish. I don't know how to explain it, but the accentuation of the words was a mixture of Latin.
The "dungeons" here seem to be basically the same as the ones in "A Returner's Magic Should Be Special." In that, they are a recreation of past events of the world, and the goal is for the user(s) to change the "ending" as it were.