Humanity had no other alternative but to stand up to the arrival of shatters in the air, also known as dungeons—and the monsters that accompanied their existence. Approximately half of the world's population perished as a result. Those who could stand up to such monsters eventually appeared, calling themselves hunters in honor of those who passed. Since then, those with the ability to wield mana and cast magic have been referred to as such. They also possessed stronger immune systems, so even a monster's pathogens, which scientists believe to be the cause behind the population's rapid descent in numbers, couldn't affect them. They were simply different.