For a series running twenty-six years, One Piece sure knows how to keep introducing fresh mystery into the adventure. When the great ruler above all, Imu debuts in the series, it throws off everything known about the balance of power. Realizing that there is someone even above the Gorosei authority means that the Celestial Dragons themselves are distractions. So, what could Imu be, and what is their purpose after eight hundred years? Let’s talk about every theory on Imu we found so far!
Who is Imu?

That’s what everyone wants to know! Imu is the leader of everything in the World Government, though they do it from the shadows. Nothing is known about who they are or what they want, but they’re seen as a shadowy outline, standing tall with a massive, pointed crown seemingly atop their head. They stand high in the throne room of the Gorosei, showing that although the twenty families said nobody would sit there, Imu is above everyone.
The only thing clear is that Imu is the one who wants everything to stay as is. They have the Celestial Dragons there as a distraction to take any kind of heat away from what they do, while keeping the idiots fat and happy above Marijoa. That works for almost eight hundred years, until the Revolutionaries finally realize that it isn’t the individual monarchies or the Celestial Dragons that are the problem. No, the one who holds all the power never steps out of the shadows, doing all their killing in secret, with no blood touching their hands directly. This is Imu, and Imu means to make it stay that way.
The Gorosei

The Five Elders that sit above the world in Marijoa and make decisions for all of those below. They lead everything with the final say over any decisions made at the Reverie, even the decision to abolish the Warlords of the Sea. When they were first introduced, they seemed to have a fair but hard stance on the things they had to do, making difficult decisions that weighed on them. Except not anymore because not everyone on Egghead Island knows Jay Garcia Saturn is a total monster. The Godhead of Science for the Gorosei doesn’t hesitate to blow a Marine’s head off with one look, and he was usually one of the milder ones.
To think that there are five of the Gorosei with similar abilities to this, yet they’re all terrified of Imu who has a similar power, is what blows minds. If all this is behind the Gorosei, then what makes this one person strong enough to leave them all in fear? They literally cower before Imu, and the silhouette Imu has in Sabo’s flashback is monstrous.
Nefertari D Lili

This is what brings things to a head, as when Nefertari Cobra finds a letter from his ancestor Nefertari Lili, it leads to questioning. He asks the Gorosei about it, who note that Nefertari Lili was present all those years ago, but decided to not become a Celestial Dragon and instead return to Arabasta. Things take a turn when Cobra reveals that there is no record of Lili ever returning to Arabasta, and her legacy is a mystery.
As far as what this means for Imu, that’s up in the air. It earns Cobra an audience directly with them though, and leads to Imu giving the Gorosei the kill order on Cobra. It doesn’t take long, and they do terminal damage to him before Sabo can arrive and escape. Hopefully, the letter from Cobra to Vivi will explain more when she finally gets it. Some theories believe that Lili actually is Imu, while others believe Imu killed Lili at some point in the past.
The Void Century

Probably the longest-running mystery in One Piece, the Void Century has been a subject of interest since the Poneglyphs debuted. They hold the secret not only to the One Piece, but to the Void Century itself as some contain historical records from the time. It’s these that Robin is after in the beginning, and it’s become a prime goal of every pirate crew lately to get the Road Poneglyphs, at least.
According to Rayleigh, he knows the full secret of the Void Century and everything involved thanks to his trip to Laughtale. This means that he could potentially have information on Imu that the others don’t, and could possibly help the others outside of the pirate world prepare. He was last seen on Amazon Lily after all, and that would be a great place to stage a defensive since it’s in the Calm Belt. No doubt the Void Century contains plenty of events that make Imu and the Gorosei look like the monsters they are though.
Immortality Surgery

There’s no way something as major as the immortality surgery would come up just to be dropped and never talked about again. At least, hopefully not, because it would be a huge waste of a Chekhov’s Gun that Oda is losing out on. The Immortality Surgery was first mentioned in Law’s backstory, as he got the Op-Op Fruit that Doflamingo intended to use for his own immortality. That doesn’t quite work out though, as Law eats the Fruit before Doffy can get it, but since Devil Fruits are constantly reincarnating, it could have happened earlier.
There’s a very strong possibility that Imu is immortal, alive since the Void Century. As things go, this is the best bet on how that happens, and for the Gorosei as well. Each of them looks different in age, with some older or younger, so it’s not a stretch that they each had the surgery done. With their resources, it would just take hunting down the Op-Op Fruit every time it reincarnates.
Joyboy

From everything known so far, Joyboy was the one great enemy of Imu during the Void Century. The giant Straw Hat under Marijoa backs this up, as well as the many differences between Joyboy and the Void Century. There’s no telling why they were at war though, or if Joyboy was there first. Perhaps Joyboy attacks Imu in the first place, wanting to free those under their control. There’s also the possibility that Joyboy was a former servant of Imu who broke free from his chains.
The biggest evidence for this is simply the Sun God Nika’s reputation as a liberator. He was known to bring joy by freeing slaves, and if that’s what Joyboy did, then Imu wasn’t a big fan considering how slavery is still around. Then there’s the matter of Saturn’s reaction to Gear Fifth in the most recent chapter, as he seemingly recognizes the form of Nika as familiar.
The mysteries of Imu will hopefully get a little more clear in the coming weeks. One Piece is wrapping up the Egghead Island Incident with the first show of power from a Gorosei, so things are heating up. With the number of lore dumps happening throughout this arc, expect either the next one or the end of this one to shed major light on the character of Imu and their motivations.