Somewhere in the Ihor Continent, deep within the territory of the United Nations of Prayn Terish.
High Priest Khardroth from the Calamity Church, after massacring one of the larger cities of the United Nations of Pray Terish, carried the same thing with a few other cities across their territory, mainly to gather at least 10 million souls from the ordinary humans.
Calamity Church was one of the more unscrupulous factions that didn't really care about their public image or anything, and they committed one atrocity after another. Just like in this case, which of course, immediately sent a message to other powerhouses who came from the outside that the Church was operating on the Midnight World.
Because these souls were very weak, people from they were, were just ordinary creatures without even a single Level as the consequence of lack of Mana, so if the priests from the Calamity Church wanted to summon some Legendary Level Fiends from the Abyss, they needed high number of the souls.