The mist of The Shadow Isles

So for a while I have had a certain thought about the mist of the shadow isles. The mist above the Isles is a big mystery right now. It seems to consume a part of someone's soul, to an extend where only a wraith remains from what used to be a creature in the past. I was thinking to myself, why would the mist consume living souls all the time. I came to the thought: What is the mist again? It's a spell used by the man now known as the ruined king.

Now I came to a thought: What if this spell is the summoning of a spirit, maybe even a demon. I checked if something like that has happened before, and it did. Xerath his lore states that he summoned elemental spirits to create a storm. So what if the ruined king did the same thing but then with a spirit that forms a mist, and that needs to consume souls to stay alive as some kind of fuel. It would explain why a harrowing is necessary. The mist needs to stretch out to get some extra souls as fuel. Is this theory plausibel, or are there parts that raise questions? I'll be glad to answer anything that all of you have questions about! Greetings, Satan Mastur