[OP: ]
The labyrinth of Malacus didn't have any monsters in the outer area where the academy test takes place after the headmaster cleared it the first time. However, being a place with grand natural Mana pools, leaving this place just like that was too dumb of a decision.
"And, the headmaster was in no way a dumb person."
He knew how to use things perfectly since he had the experience and knowledge of eons of his work as the 'headmaster' of all the great academies in this Worldline.
"He knew perfectly well what to do with the great Mana this place generates so, he did three things to make the best use of this free resource."
First of all, he created strong magic arrays throughout the labyrinth to seal off the actually dangerous areas like the core of the labyrinth which still contained that certain grimoire as well as traces of its previous owner and her children.
