Difficult Mission
Eradicating the demon species would not be easy. These creatures were very skilled in their regeneration and could live much longer than beings of other races. That is, while the few specialists who could eliminate them had a short time to act against them, these beings could torment different generations.
They knew very well how to hide. When needed, they disappeared from the world for millennia, sometimes long enough for some specialists to die of old age.
Because of these special characteristics of demons, even in low numbers and even considering the long history of hostility they had with other beings, they still existed in this world.
So even though the number of demons to be killed for this purpose to be achieved was not so great for Concordia's killing scale, this was a high number of dead demons for someone to achieve in life.