Originally Posted by
Ivan the Fourth's Profile
While the Ivan the Terrible of the Pan-Human History was indeed a tyrant, he was an existence without any connections with magecraft.
In the Lostbelt however, he invited the magi when the crisis of global freezing became imminent.
He sought the path for survival that came with the techniques for fusing humans with magical beasts.
However, that was the same as bringing to this world lifeforms that were completely different from humans already. So, when even their mentality ended up changing in the end, they were perceived as a human history that had reached an impasse――― a world that had to be pruned.