[The Rays] LC arc chapter 13 & 14 - Origin lore
This took some time to wrap my mind around. I even had to ensure AE's side about Underworld won't break it for me before posting it as I tried to write down all the facts they gave us up to date.
ToB happens in a distant future AFTER those who wanted to descend descended and the whole world got cursed by those who refused to do so and Arthorius is this much of a trouble for Yalanda endangering the world's stability because he is a pact holder WITH THE SAME BEING Mithos has a pact with. The last chapter was all about it. Now try to imagine this being is Aifread's creation. Something is still off, right? Off to the point Balore laughs at the fact Aifread is revered as a god now.
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So, who were they originally who cursed the world? Who even has enough power to bend world laws THIS much?