That's funny as hell, I started working on a theory last week that Lily helped create the Poneglyphs. No need t finish it now, but I guess I'll post what I was going to, here....
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With all the possibilities of what could have happened to Lily after the events of the 19 Kingdoms settling into Mariejois, there is one avenue yet to be explored. That is the simple fact that Lily herself relinquished her throne in Alabasta, and set off on a journey. Now there could be a multitude of reasons for this, but I think the one that fits narrative direction the best, is the simplest one, where she set off to tell the story of what happened during the Void Century.
Think about it for a minute. The person who created the Poneglyphs havd to have extensive first hand knowledge of everything that went down before and after the war between the 20 Kingdoms and the Ancient Kingdom.
Now many people believe it was entirely Joyboy who went around and created all the Poneglyphs, but that currently does not make a whole lot of sense. The assumption is, is that Joyboy was the King of the Ancient Kingdom, and after losing the war, he went around creating the Poneglyphs, to keep the History of the World in tact.
The problem is, is how would Joyboy have known that there was a plan to erase the events of the Void Century? The only way he could have possibly known that, is if someone who knew about the plan, told him.
And that's as far as I got.
vs 
