So…uh…anyone know what The Harley is talking about?
Safe to say the Harley’s passages matches the mural. Let’s assume each area of mural under a Harley passage represents that particular message. If so, let’s try figuring out what’s going on based off of what we currently know about the One Piece world and its past.
The First World
Ok… Ah, the Mother Flame. Cities. …Maybe the world was advanced and that civilization discovered the Mother Flame. Things went downhill from there and somehow the planet was destroyed. Remember, we recently learned the One Piece world was destroyed twice. Once during the Void Century and the other, I presume, was way way WAY back in an advanced age.
If the Sun God is Nika, then the Earth God was Imu? Or, whoever had the Earth God powers during that time? And does all this earth talk symbolize the creation of the Red Line and it subsequent separation of the planet into four blues? Sure, let’s go with that.
The Second World
“The Forest God tamed demons” could mean during this low point in history, devil fruits somehow appeared in the world and were used to fight the demons? [Wait, wait, wait! Does that mean demons were unleashed because the ancient civilization dug too deep for the Mother Flame and awoke them? Like when the Dwarves in Lord of The Rings mined to deep and awoke the Balrog? Hmm…]
Those of the half-moon and moon dreamed? Hmm… Lunarians and…some other race of people, I guess. The sea god storming could mean devil fruit users gaining their water weakness. If so, it’s interesting something happened to give them that vulnerability rather than it always being there.
The World Tree also plays a role here but I’m not sure what that was. Unless… Were devil fruits born from it?! Devil fruits originated on Elbaph. A place where horned giants that could be mistaken for demons lived and has an area they call the Underworld… Fascinating!
We see flying arks in the mural similar to the one God Enel built (no doubt from ancient blueprints he found or stole somewhere). Did the Lunarians and others escape the demon infested planet in order to live peacefully on the moon? If so, are they still there? I don’t think it was ever confirmed if anyone was still alive up there except for the Space Pirates before Enel got there.
“Man killed the sun and became god” I take that as Team Imu (the united countries that founded the World Government) attacking the last remnant of the formerly vast ancient civilization (now only one island, Laugh Tale), flooding the planet, and taking over the world. Imu later moves into the Lunarians abandoned territory atop the Red Line and creates Marijoa. Basically, The Second World describes what happened during the Void Century.
Mammoth Base Opera Castle 