I'm waiting for my future time-traveling Mistborn self to come back in time to tell me that I'd be rich, handsome, and have a concubine. Get it together, future self! Jeez, the nerve of these time-traveling Mistborn.
Maybe darxbane, you are like an Elantrian. Dead, but you don't know it, lol...
We really need to get back on topic... so, I'll begin with a theory:
I came up with great story idea... about a prophet and things. That got me thinking: someone had to create the Terris Prophecies to begin with. Perhaps a Worldbringer did... who knows? However, Brandon constantly refers to the "mythology" of the Mistborn world, where there is two forces in the world and there is only a single mist spirit. Obviously, we know this refers to Ruin and Preservation.
I don't know about you, but I don't think the Terris Prophecies are created by a Worldbringer. It would kind of be anticlimactic. Some people think that Ruin completely fabricated the Prophecies, but I don't think so. A Feruchemist would know if in his coppermind, he suddenly found a giant thing of prophecies.
"Dude, dude! Guess what!"
"Yeah?"
"I discovered the Terris Prophecies in my coppermind, man! We're saved."
"You're on crack."
Obviously, something like that would be rather suspicious. The same with Ruin creating a prophecy from manipulating paper. Say you have an empty book, and then the next day, it turns into a whole book of prophecies. That would be equally freaky, and make people want to burn the book.
Let's imagine, then, that Ruin wants to destroy the world, because that's what it does. Now, because the Prophecies existed before the Ascension, and that it mentions the Deepness and stopping it, we can presume that the Deepness existed before in some form.
This is all supposition, but what if Ruin originally tried to destroy the world with the Deepness as a direct way to destroy the world? There could be a time where there were no Prophecies. Something had to spawn these prophecies to begin with.
If the Prophecies, before this "basic-Ruin" didn't realize it would be more efficient to manipulate them, had an innate knowledge on how to defeat the Deepness/Ruin, this suggests a more enigmatic force, a force which is more knowledgable about the whole dichotomy between Ruin and Preservation. Presumably, this points to Preservation originally creating the Prophecies.
Now, Kwaan's account tells us a lot about how the Prophecies are manipulated. First of all, the Terrismen already had a vague knowledge of the Prophecies (because Ruin couldn't just create a string of prophecies without scaring people, regardless of whether he has the power to do so or not). Kwaan calls the fact that Alendi must, supposedly, go free the power like a "moral imperative". But before, he says "they were more vague." This is extraordinarily important. It means that there was a time--very recently, if Kwaan can remember how it originally was--when the prophecies were not being manipulated.
Follow my reasoning: if the Prophecies had been manipulated for hundreds or thousands of years, they would be so corrupted that Kwaan would have no question that Alendi would need to give up the power. Ruin would be subtly changing them for a long time into the Prophecies were perfectly correct for Ruin's intentions.
However, it's not. This gives me further reason to believe Ruin didn't create the Prophecies, because Kwaan wouldn't realize the manipulation if it happened centuries ago (remember, Feruchemists didn't live forever, so Kwaan couldn't have lived for centuries). This points to a recent event that somehow triggered Ruin to manipulate the Prophecies. The Deepness also appears to be a recent event, or else the Deepness would already have destroyed the world.
Something that we don't even know about yet, before the Ascension, happened to trigger Ruin to both of these things in the span of one lifetime (Kwaan's time). As our understanding of Ruin and the Lord Ruler goes, the Lord Ruler did something to weaken substantially Ruin. No Lord Ruler and Ruin gets stronger. Obviously, in Kwaan's time, there was no Lord Ruler, so ostensibly, Ruin could go out any time, summon the Deepness, and manipulate the Prophecies.
He didn't. Now, Ruin is our ultimate incarnation of destruction: if it could destroy the world, it would. It wouldn't wait for centuries until this time to unleash the Deepness unless: 1. It couldn't. Or, 2. There is a better reason to destroy the world then (?).
Something is going on here... something far greater than we know.
(By the way, I think this is as good of topic as any for Hero of Ages and Terris Prophecies)