As with most of my theories, this one’s going to be a little out there, and a little wild but stay with me - the conclusion is pretty fun.
For this theory, I’ll answer six questions.
But first, let’s talk about Gods and Devils.
In One Piece, the concept of turning things upside down is really important. This is what Roger famously said when he met Rayleigh.
Turning things upside down applies to many things - words, concepts, ideas.
What do you get when turn the concept of ‘God’ upside down? The Devil.
Question 1: Why is God Valley important?
It's important because it's where Devil Fruits come from. This is not an original idea - @3SkullJoe has a great thread about it which I’ll link at the end.
If you think about it, every Mythical Devil Fruit can be connected to God Valley.
Now - you might be thinking, if Devil Fruits are from God Valley, does that mean that there is some sort of Devil Fruit tree there?
No, I don’t think so. I think Devil Fruits don’t grow on trees. Devil Fruits are made.
(Just like the Fruits made by Smiley, but more magical.)
Question 2: How are Devil Fruits made?
I believe Devil Fruits are made using the Cornucopia, or the Horn of Plenty. This is a horn that can turn one’s dreams into reality, in the form of fruits that grant powers.
The Devil Fruit Horn has been hinted at in the story all along - it's the spiral we see so many times in One Piece - even in Oda's signature.
The Devil Fruit Horn was was kept in God Valley, where it was used to make Devil Fruits.
These Fruits were given to fighters in the World Government and the Marines. For example, the ones that were given to CP9 and Sengoku.
Some of these fruits were taken by the Rocks Pirates.
(An aside - the God’s Knights have that name not only because they serve God/Imu, but also because they get their powers from fruits that came from God Valley.
Note the similar swirly patterns in the scene introducing them, and the scene where Kaku and Kalifa were given Fruits.)
Question 3: What do you need to make Devil Fruits?
With great power, comes great sacrifice.
Islands are destroyed at a whim. Slavery exists. People get turned into toys, lose their shadows and go hungry on the regular.
The world of One Piece is a cruel place.
In Punk Hazard, children were experimented on just so Caesar Clown could figure out gigantification.
I think something similar was happening in God Valley.
Devil Fruits were being created using the dreams and desires of children.
How this might work -> brainwash a child into wanting something, or wanting to turn into something, like a giraffe. Blow the Horn, turn their dreams into a fruit. Voila.
Vegapunk himself had linked dreams/desire with Devil Fruits.
Devil Fruits are the dreams of dead children.
Why children, and not adults?
It can probably work with adults too - but a strong theme in One Piece is 'childhood dreams'.
The dreams you have as a child tend to be the strongest - kinda like how for most of the crew, their dream was established when they were children.
Question 4: What does Rocks have to do with it?
I think Rocks took his crew to God Valley because they (a) wanted the Devil Fruits that were there and (b) wanted to seize the Devil Fruit Horn for himself.
The 'taboo' Rocks was pursuing was related to Devil Fruits.
We know that Roger and Garp were also at God Valley.
I believe that Roger landed at God Valley first and started causing havoc.
Rocks, much like Blackbeard in Impel Down and Marineford, arrived later, seizing upon the opportunity.
Unfortunately, Roger and Garp teamed up against him instead.
Up against the juggernauts of yesteryear, Rocks was faced with defeat.
Question 5: What happened to Rocks?
Okay, this is where this gets a little wild.
Rocks, up against Roger, Garp and maybe some members of God’s Knights was on the verge of defeat. Perhaps, even death.
Instead of letting himself be killed, he did something few have done.
He blew on the Devil Fruit Horn himself.
In the face of death, the 'D' somehow has the last laugh.
Here we recall quotes from Hiriluk, Roger and Oden.
"You can't kill me! When does a man die?"
"I won't die partner!"
"My soul will live on!!"
Rocks forfeited his life and turned his dream into a Fruit. The Hito Hito no Mi, Model: Rocks D. Xebec.
So to recap the answers from our five questions:
- God Valley is where Devil Fruits are made using the Devil Fruit Horn, which turns dreams into fruits.
- Rocks went to God Valley to get the Horn, but instead of escaping, he used it himself.
"People's dreams don't ever end!"
Question 6: What does Shanks and Buggy have to do with this?
We know that they were possibly found at God Valley.
There’s a few possibilities - they could be children who were to be sacrificed, children of Xebec, children of Celestial Dragons, or even children of God’s Knights.
What we do know is this - Roger found them.
Since he found them, I believe that just like how Roger named Laugh Tale, Roger named Shanks and Buggy.
Fittingly, Roger named them after the Devil Fruit Horn.
Buggy, after the Bugle, and Shanks, after the Shankha (or conch)!
I believe that Buggy and Shanks’ true importance is not limited to the One Piece.
Their true end point is the Devil Fruit Horn, which has been moved from God Valley.
The Devil Fruit Horn and the treasure of Mary Geoise that Doflamingo spoke of are one and the same.
Going back to a point I raised earlier - if Rocks did become a Devil Fruit...where might he be?
Actually, there's another character who might be named after a horn.
Danaë is a figure from Greek mythology. An oracle predicted that her son will kill her father. This led to her father imprisoning her in a tall brass tower.
However, Zeus, the king of the gods, desired her and impregnated her. Soon after, their child Perseus was born.
Perseus went on to become a hero - slaying the Gorgon Medusa and the sea monster Cetus.
Ultimately, he fulfils the prophecy - in a way that's typical of Greek tragedy, he kills his grandfather by accident.