A newer theory on kaeya (after the new archon quest) Right so, there were theories on kaeya being an abyss mage because of his abilities and aesthetics, also people said the fact he is from khaenri'ah is suspicious, but now that we know that the only other person who is from khaenri'ah (Dainsleif) is the twilight sword who failed to protect khaenri'ah,in other words, now we aren’t sure if khaenri'ah exists anymore, so my theory is that kaeya is also not human nor an abyss mage, he is possibly the ‘great sinner who created endless monsters’ , and ofcoarse that also makes him immortal.