Lore theory about version 2.8 obvious spoilers.
>!First of all I want to mention ether manipulation. The mc has been capable of manipulating ether to an insane degree. That being curing vivian and immediately mastering the teachings from yuinque summit.!<
>!Second is that the condition only began after saving ye shuanguang, now whether it's from the energy of the quingming sword or the residue of the creator is uncertain tho im 80% sure its the quingming sword.!<
>!Third is how remeiel described the condition as "two sides fighting for control, you were already sliding into the abyss, thaumiel only exellerated it." Not the exact words but I hope you get the point. It seems that either way the mc was going to turn into an ethereal either way.!<
>!And fouth is that judging from wise and belles conversation after talking to velina and norma.!<
>!the "incident" was also the mc, seemingly causing or atleast connected to the fall of the old capital. The exact wording was "back in the hollow, i-i dont know why but, i just had to touch it. That void hunters weapon... and the moment i touched i think i blacked out but i could feel it. Like i was back in that same state as before.... teacher... that incident i caused... it never really ended."!<
>!Also considering the boss is called "phaethon of the scorched horizon" plus the whole eclipse thing during the boss fight and that the mc is a student of helios academy the mc might have the power of the damn sun.!<
Also I am terribly sorry about miswording. I'm terrible at remembering the names of people and locations.