Summary
Gol D. Roger’s treasure is called theOne Pieceand is also what the legendary series is named after. Ever since the very first scene of the series which showed Roger’s execution, pirates from across the world have been in search of this elusive treasure, all while fans and characters in the series have been wondering about what it even is in the first place. There are many theories, such as those that claim that it is a Devil Fruit!
Devil Fruits are the main aspect of theOne Piecepower system and throughout the series, fans have come across many that are incredibly powerful. These fruits belong tosome of the most powerful charactersin the franchise, so, naturally, many assume that the fabled treasure of legend could be something similar, but with power far beyond that of any other fruit. So, let’s take a look at this theory!

The Most Powerful Fruit Of Them All
Now, if the theory of theOne Piecebeing a Devil Fruit ends up as true, then it would not make sense for it to be anything like the others that fans have been shown in the series. This Devil Fruit would be exceptionally powerful, so much so that possessing it would make its userthe unequivocal Pirate King, which would make sense considering that Roger was the only King that the world had ever seen.
As for the type of Devil Fruit that it could be, there are a few theories regarding it. While most probable that the nature of such a fruit would be unlike anything that has ever been shown before, it could also very well fall into any one of the 3 Devil Fruit categories, since they all have the capacity of having incredible strength.

These Devil Fruit users are always so dependent on their special abilities.
The Sea-Sea Fruit
One thing that most fans of the series agree on is the fact that theOne Piecewould make the one who found it the ruler of the seas. If it is,in fact, a Devil Fruit, many believe that it could allow the user to control the sea, making it a power that can dictate and control the events of the entire world! This is because everything in this world is based around the ocean, since civilizations are spread across innumerable islands and the main method of transport is ships.
Due to this, if someone can control the sea itself to do their bidding, they effectively control the entire world! This fruit can be a Paramecia type that just outright lets them control the waves and everything to do with them, or even a Logia type that lets them become and fully control water. Such an ability would also put them above everyone else, since the main weakness that Devil Fruit users have is seawater. This is a power that can even keep the strongest Haki at bay!

Time Travel Fruit
Though this is a theory that is very weak in terms of context, some fans believe that theOne Pieceis a Devil Fruit that allows time travel. Though there is very little reasoning behind this theory, proponents believe that upon getting this fruit, Luffy himself would eventually goback in time to the Void Century, where he would take on the identity of Joyboy!
There is little context here, though one of the main reasons behind it has to do with the Straw Hat’s first visit to Long Ring Long Land. Upon reaching the island, the crew met and saved Tonjit from his stilts, where the very first thing that he ever said to them implied that he recognized them somehow but was promptly brushed off. This theory states that if Luffy does become Joyboy, he plants the seeds for everything to work out the way it does in the story.
A Likely Devil Fruit Theory
When it comes to theOne Piecetreasure and Devil Fruits, the most probable relation to be made is that the treasure itself isthe fabled Devil Fruit Tree. Though this theory is an old one and most fans of the series believe it to have been debunked, it would still make for an incredibly valuable treasure that could also control the world in a way.
By controlling the flow of Devil Fruits and essentially dictating the power system of the entire world, one could easily become the most powerful person on the entire planet. They could control armies of Devil Fruit users who could have access to Paramecia, Zoan, Logia, and Mythical Zoan Fruits, marking the single greatest threat to the World Government that the series has ever shown!
I once heard that the Devil Fruit’s are all the Sea-Devil’s incarnations!
However, this theory should also be taken with a huge grain of salt. This is mostly because there isn’t much context behind it, so this theorizing is entirely just guesswork until some solid facts are given. However, this is not to say these theories don’t make sense, sincethe entire journey to the treasure itselfalso comes with the reality of the true history of the world, already making those on the journey there incredibly important.
So, this is why theOne Piecebeing a power that allows the user to control the world in some way makes so much sense. This also bleeds into why the World Government wants all the knowledge regarding these things suppressed, perhaps even living in fear of what would become of them and their world if the user of the ultimate treasure would free everyone is against them!
One Piececan be streamed onCrunchyroll.
One Piece
One Piece is a Japanese manga written and illustrated by Eiichiro Oda. The series follows protagonist Monkey D. Luffy and his Straw Hat Pirate crew as they explore the Grand Line to find the King of the Pirates' ultimate treasure, the One Piece, to become the next king. The manga’s popularity helped it spin off into a larger media franchise, including an anime with more than 1,000 episodes.