This theory is quite strange(and not mine,i did only some changes) but it is made with a lot of proves!(sorry for the fail english)
THEORY:
it's about the INHERITED WILL AND THE VOID CENTURY(about from the middle of the text and after the one piece is explained)
Let’s summarize things first :
As we know, there was an age called “The Void Century” in OP’s world timeline. Except Roger’s pirate, not a single living soul on this planet have any idea what the really happened within that gap.
However an Oharan archelogoist, Profesor Clover, had a slight hint about it. He told us that in that time there was once stood a prosperous and powerful ancient kingdom that ruled over the ocean. However, They had a certain enemy. This enemy felt threaten by the kingdoms existence and their certain ‘policy’. So then they invaded the kingdom and succeded. The kingdom was fallen to shred and somehow, the enemy managed to wipe out every single information about them from history.
Coincidentally, The end of the kingdom’s reign also marked the end of The Void Century. At the same time, an organization called The World Government was built for the first time. Clover had a theory that the WG was none other than the enemy itself.
Now let’s enter the theory :
"THE HIDDEN PATTERN"
“
There are 3 things that cannot be stopped :
Men’s Dream
The Flow of Time
Inherited Will
As long as people continue to seek the true meaning of freedom, they will never ceased to be!
”
-- Gol D. Roger --
As these words first appeared in chapter 100, they seems pretty meaningless tome. I took them as nothing more than some random cool quotes.
However, as sthe story goes deeper, I realized (and some of you might have figured it out as well) that One Piece story has been consistenly following those 3 things : Man’s Dream, The Flow of Time, Inherited Will.
Let’s see :
1. Hiluluk's Sakura
Hiluluk had an impossible goal, and that was to create a panacea capable of curing all kind of diseases or ilness. however his experiments were keep failing and failing for 30 years. though eventually, Hiluluk's Sakura was bloomed, it is still not a miracle cure. Chopper who greatly respect to Dr. Hiluluk inherited these will by setting sail and joining Luffy.
2. Golden Bell of Shandorian
Two best friends parted away on the shores of Jaya. Their friendship didn’t end here, they promised to meet again someday. Calgara kept ringing the golden bell so his friend wouldn't get lost in his way there. Unfortunately, the fate decided to send Island of Jaya 10.000 m above the sky. Calgara died in the war, while Norland was executed in his hometown. Their promise were totally buried.
400 years later, a boy named Luffy succesfully found and ring the long lost bell, thus fulfilling the forgotten promise.
3. All Blue
Zeff wanted to find the legendary all blue, but a year of sailing the grand line hasn’t bear him any fruit. However he was still pretty assured that the ocean exists somewhere in this world, so he inherited his dream to Sanji, hoping that Sanji will achieve his dream someday in the future.
I only picked 3 examples, but there are actually more of them. So, anyone captured the big picture I’m getting at? or not? well, Here is what I meant :
1. in the past, there’s someone who had a certain dream/desire/promise, but for a reason or two they didn’t manage to complete it (Man’s Dream)
2. the dream was delayed for many years (The Flow of Time)
3. Eventually, there will be someone in the future who will complete his/her dream (Inherited Will)
That’s right, starting from the first chapter up till now, the storyline has ALWAYS been following this very pattern. I’m quite surprised myself, we’ve been through this pattern over and over again, though I’m sure fery few people are awared of it. I call it “the golden pattern” (because Gold Roger created it).
This made me think, wouldn’t Roger has the pattern of his own as well? My curiosity was finally answered in chapter 576.
So apperantly Roger had this will, a will that has been inherited for hundred years. And he waited for certain somoene to carry on this will… somehow it also has something to do with One Piece.
So what’s is this all about? What was Roger’s will exactly?
"ROGER’S DREAM"
The Golden Pattern (starting from here everything is 100% theory)
MEN’S DREAM
Roger’s will that Whitebeard was talking about, it actually wasn’t his original will. Roger inherited it as well from waaay back then, from 800 years ago to be precised. Yes, it was originally the will of The Ancient Kingdom (let’s call it AK from now on).
The AK was a big kingdom, it ruled over almost the whole world (just like WG does now). They apparently also had a pretty-advanced civilization. One could say that there’s almost nothing they couldn’t achieve with everthing they got at the time.
However they had an issue. As we know, the planet of OP contains of big four seas, east, west, north, and south, each were separated by the Red Line and the Grand Line. The AK saw Red Line and Grand Line as a big obstacle because they have been been preventing people from traveling from one sea to another, thus preventing the AK from reaching its full prosperity as well.
And So they made this project, an insane one, but has to be done. The project was about eliminating the Red Line and Grand Line to fuse the 4 seas into one big ocean, the united ocean. The called it the project of “One Piece”. In order to do so, they started to build some weapons which will be strong enough to destroy the red line (later called Ancient Weapons)
It turned out that not everybody was pleased by this project.. you know, politics. Some other kingdoms were totally against it, they smell a conspiracy was playing behind it. But the AK stood their ground no matter what. Guess what happened next? a huge war broke out. It’s the AK vs 20 kingdoms who were against the prject of "One Piece”.
The 20 kingdoms came out as the victor and they declared themselves as The World Government. Meanwhile the AK was reduced to shred, along with all their historiy, and the “One Piece” project was never heard again since then.
THE FLOW OF TIME
Unexpectedly, The AK has anticipated their downfall. Before the war begun they had carved historical notes on these certain metals which as hard as diamond(later called the poneglyphs) and hid them throughout the world, along with the weapons they’ve built. The AK really wanted to make sure that their desire wouldn’t die in case of anything bad happened to them.
the WG was mad with this fact and completetely prohibit any form of poneglyph dechipering.
but it's too late, the will has been passing through ages since then… silently waiting for someone to recieve the massage.
THE INHERITED WILL
800 years has passed, a pirate named Roger sucessfully reach Raftel and discovered the true history. He knows exactly what to do, but unfortunately his body didn’t allow him to… he had this incurable disease, remember? whereas the project needs a lot of power and time to complete, 2 things that Roger didn’t have that time.
Therefore, he decided to create The Golden Age of Piracy instead, hoping that there will appear someone who is strong and righteous enough to complete the massage in his place.
Who will be that ‘someone’? I think we all know the answer.
"THE PROJECT OF ONE PIECE"
Now… how exactly does this project work? Will fusing 4 seas into a united ocean make Luffy’s journey worthy?
Let me explain it… It’s gonna be a bit technical so I’ll include some ilustrations.
So here is roughly how the globe looks like.
Chapter 51, page 4
Chapter 71, page 4
And this is the flat(word?) version :
The idea of “One Piece” is to create a united ocean, a perfect ocean to sail. Therefore we have two jobs : fusing all the seas into one and eliminating Grand Line abnormality. GL’s abnormality? Is that even possible?
Apparently it is possible for the AK scientists. The trick is destroy a spot where every sea on the planet (north, west, east, south, grand line, new world, and calm belt) meet in one place. There is a spot like that? Actually, there are two, and both need to be destroyed. The two spots are reverse mountain and mariejoa/fishman island.
a simple ilustration :
And here is the meeting spot, the circled area one :
Think for a moment there… It made sense right? Mariejoa/fishman island also has a similar geography (minus the reverse canals).
The meeting spot are set. Next, the ancient weapons will do their job : annihilating those spots.
Ok let’s do it to reverse mountain first… FIRE IN THE HOLE!!
Even with the mighty power of the ancient weapons, the annihilation must be calculated and done correctly to get the wanted effect. If succeed, this what will happen next :
Losing a huge mass of land, The sea became even more unstable than before, a big whirlpool will appeared on the center of destruction spot, storms and tidal wave occuring everywhere. However they’re only temporary, after a couple days the raging storm shall be subsided.
And then, the magic began…
disastrous random-weather on grand line and NW suddenly doesn’t occur anymore
the magnetic field which make a normal compass useless are completely gone
Even the wind starting to blow on Calm Belt
How about sea monsters? Well, this is the time where Poseidon come to play. The Poseidon has fully taken control of the sea king and make them some kind of ‘police’ of the ocean to prevent other sea monsters from going wild. (yes I do think this is very possible)
The ideal united ocean is finally created . The project of One Piece officialy succeeded!!
But is that it???
It’s not. There’s actually one more after-effect, and it’s the most important one.
The big whirlpool that appeared after the destruction of reverse mountain, It happened because the water mass of the four seas simultaneously flowed into the center of destruction -- the place where reverse mountain was stood once. Logically, that means every kind of living things which originally lives in four seas were brought there as well. You literally could find every fish species from all over the world here.
Wait, was that sounds familiar? Exactly, the destruction spot has became that legendary mythical sea…
The United Ocean and the legendary All Blue
At least 6 of Strawhats’s dream will be accomplished because of these achievementt.
Luffy -> he wanted to be the pirate king, “the man who has the most freedom in the ocean”. now that the ocean has been united, Luffy has literally achieved this feat.
Sanji -> it's obvious, he finally found the All Blue
Nami -> now that the entire ocean is free to sail, drawing world map is not so impossible anymore
Franky -> same reason with Nami, Sunny now can travel all over the world
Robin -> all of this happened because she found out the true history
Brook -> Ever wonder how Brook will return to the Twin Cape to meet Laboon? It seems impossible because the reverse mountain was in the way. But now, it’s GONE! They’ll meet again with ease, Bink’s Sake will be played along their emotional reunion. It will be a perfect moment.
How do you think??
Now how about the spot at mariejo/fishman island ??
“THE PROMISED DAY”
This mermaid… she didn’t lie at all. nor she’s wrong. She was actually foreseeing the event we’ve been talking about : the project of One Piece. And It is indeed Luffy who will trigger the event.
The ancestor of FI were actually well awared of this upcoming event.
How so? Here’s another theory : Joy Boy, he was actually the king of the AK.
Ok I know that sounds so random. There’s a theory for that but let’s save it for later…
Like a said, destroying both reverse mountain and fishman island is a must to complet the project. Therefore, King Joy Boy made a proposal of destroying FI to the former mermaid princess, Poseidon. She agreed but as an exchange she asked Joy Boy to move her people to a better place on the surface. Joy Boy gave a nod and started building Noah Arc afterwards.
Joy Boy managed to finish Noah but short after his kingdom lost a great battle against the 20 kingdoms. The promised cannot be fullfilled and he apoligized to Poseidon through poneglyph. However he still promised her “that day” would eventually come in the future, the day when fishmen and mermen live under the sun.
(You see that Oda used the another “golden pattern” again here)
Conclusion : “The promised day” and madam shirley’s prediction, they are actually the same thing.
The scenario is pretty simple : at “the promised day” Luffy will trigger the attack on the destruction spot, but before that, Shirahoshi will command the seaking to move all of the FI’s citizen to a safer place (by using Noah).
Once destroyed, the same magic which happened to reverse mountain spot will also be happened here. The All Blue will appear, replacing the destruction spot. mermen and fishmen will move here later and make a brand new civilization around the Sunny Tree of Eve (if Sunny Tree has the same reputation with Adam tree, it will completely survive the destruction. There are ilustrations for this but I lost it somewhere ).
Meanwhile, this also marked the end of WG’s reign because Mariejoa --the prime symbol of WG-- was buried alongside FI in the process. Luffy finally won his war against the WG.
If you look from above, both mariejoa and fishman island are located on the same place. Destruction are inevitable for both.
A = Sunny Tree of Eve
B = the Red Line
C = underwater part of Red Line
D = Fishman Island
E = underwater cave
F = holy land Mariejoa
I actually had more ilustrations explaining the destruction in process, but I lost’em somewhere.
well to make it simple, everthing in this pic will be completely destroyed, except the sunny tree.
anyway, I want to add a bit more theory, about the AK.
The AK, did they really extinct from history?
In Robin’s flashback
Clover was about to reveal the kingdom’s name when he was shot by Spandine.
you know, It always seems a bit odd to me that gorosei felt threaten by revelation of the name alone. But it could means one thing : the kingdom is actually still exist until now. Gorosei are awared that people could recognize the name. Or even us readers could recognize it for that matter.
if the later was true, it means the kingdom name was mentioned somewhere before the W7 arc… let’s see, we have Arabasta, Drum, Shandora, and probably Raftel (it could be a kingdom’s name)
Beetwen the four, which one of them could be the AK? Apparently, a few facts about Shandoroa match the description of AK the most.
Shandora was collapsed 800 years ago after a big war with certain enemy (the AK was collapsed at that time as well)
Judging by the ancient picture of Bilca on the moon, the origin of Shandora, they apparently had an advanced-civilization with all that futuristic stuff (just like how Clover pictured the AK)
Shandora was once a prosperous kingdom 1000 years ago