User blog comment:ND999/Lore Hypothesis, Mt. Targon, Guardian Sea and Shadow Isles/@comment-3087008-20141115152137/@comment-3110123-20141115160013

I was also considering the "Kalsta is Lunari" theory, but I kinda gave up on that when I saw the Q&A. Although I can take it two steps further with another hypothesis.

Let's say the "Ruined King" got both the Avatar of the Sun and the Moon to his side because he wanted to gain immortality. However, instead of being blessed by the Sun and gaining true immortality, he was cursed by the moon and gained undeath. That would be why the Shadow Isles are shrouded in darkness to this very day.

Now you may ask, "why would he need a Solari/Lunari to gain immortality?" then let me ask you this: Who else uses the blessings of the Sun to gain immortality?

The asnwer would be the Shruman Ascended. And as we know, failing to preform the ritual of Ascension could result in a catastrophy. I'm just bullshitting here though, so don't take it too seriously.