Let’s start of by introducing why this is not a simple reveal down the line but a possible contradiction in the series. This is probably the first time you ever heard about this and it will surprise you how you never noticed.
“I don’t want to conquer anything”
I think you have seen it now. Luffy doesn’t want to conquer anything but uses “Conqueror’s Haki” to intimidate them. This could be a minor plot hole that could never be addressed but I use it as a hint that this might not mean what we think. It is only called “Conqueror’s Haki” after all and what it means and how it functions is a different side.
But lets extract some information out of the first ability (that Luffy possesses): Conqueror’s Haki
1. This is the ability to intimidate your oppenent
2. Whenever someone gains fame in the world, they are most likely using Conqueror’s Haki
3. Conqueror’s Haki can’t be trained/strengthened and is measured by the user’s spirit and personal growth
Now to the 2nd ability (that Luffy possess as well): The Voice Of All Creation
I could show more panels like Momonosuke (where Luffy could understand Zunisha but not give orders, its basically the same situation here) and Roger with the same sea kings/reading the Poneglyph. Its important that Luffy and Roger had this ability and therefore Joyboy as well. Its as always connected to the “Will of D.” and its a requirement to fulfill Joyboy’s will. Only those who walk Joyboy’s path can find the One Piece and that of course includes “The Voice Of All Creation” as well. Read my theory above if you doubt this at all.
Let’s see what the voice of all things does exactly:
1. It makes you communicate your feelings to creatures that you can’t communicate otherwise with.
2. You can understand the feelings/meanings of creatures/objects you otherwise couldn’t
We already see the stark contrast to Conqueror’s Haki here. The Voice Of All Creation is the complete opposite of what Conqueror’s Haki is. Conqueror’s Haki doesn’t try to understand one another, its the oppression of one another. Conqueror’s Haki forces your will on to someone in order to intimidating them. But there is already a mystery here, why did Luffy learn this ability for the first time after the time skip? Its because he trained his spirit(aka haki) and therefore we know for a certainty that The Voice Of All Creation is connected to haki. This would be a major plot hole if it just happened to activate after the 2 years for plot progression purposes solely. So keep that in mind.
Lets get into the last ability that Luffy doesn’t has but Shirahoshi does,the 3rd ability: Ancient Weapon (Poseidon in this case, to simplify I am not going into detail about Uranus theories, the points will stand either way. Due to Pluton’s nature this ability doesn’t seem related)
So how does Poseidon work? As we read above The Voice Of All Creation enables you to communicate your feelings to creatures that you otherwise couldn’t but Poseidon goes one step above. Poseidon makes you “control” sea kings without you even knowing it. Just your feelings alone and without force makes them do what you want. It is a hybrid version of The Voice Of All Creation and Conqueror’s Haki. You use your will to control your opponent but don’t intimidate them, you make them understand through your feelings.
How is this all connected?
You can’t train Conqueror’s Haki directly and it will improve once you train your haki in general. The Voice Of All Creation is haki because it was obtained by Luffy after his haki training. Poseidon is an ability that does what The Voice Of All Creation and Conqueror’s Haki does combined. Its the combination of two sorts of haki’s which concludes that its haki as well.
Poseidon = Conqueror’s Haki+The Voice Of All Creation
Now why is this important and to which other mysteries is it connected?
One being the greatest mystery of them all. What happened during the Void Century and in particular the Ancient Weapons? From my theory we know that Joyboy was allied with all Ancient Weapons(Pluton with Alabasta, Poseidon with the Ryuugu queen and lastly Uranus with the Kozuki clan). We also can conclude that Joyboy had the The Voice Of All Creation and Conqueror’s Haki. Now, is this not peculiar that all those mysterious abilities relate directly to the ancient kingdom? Was Joyboy the originator of them all? Is it connected to the One Piece? Do you need The Voice Of All Creation to obtain One Piece? Is that the reason for Joyboy’s original plan of hiding Raftel? Did he taught the first Poseidon this ability? Did he teach that ability to the Kozuki clan as well? Is that the reason why Joyboy had to die? He gave the world the power to understand each other and that is the real value that threatened the 20 nations and future World Government?
On this point I will return later because its not a coincidence that we know that Roger/Luffy have the The Voice Of All Creation and are able to understand what Poneglyphs say. Luffy has the potential to learn the true history and use the One Piece by himself. But lets not get ahead of ourselves. There is one more thing to discuss and than we will bring it all other. I talk of course about Devil Fruits.
*Theory by Donal D. Trump