Every time the Gorosei meet and discuss nefarious things, and in the only two chapters we've seen Imu, they use the term "extinguish/remove" from history.

Now, this is interesting, and I don't think too many people have thought too much into this. But that's important wording.

Let's examine a few things:

• NOBODY knows anything about the void century, except for Roger and his crew, and a few other select individuals, such as the scholars of Ohara and Robin. Some of the Yonko and higher ups in the WG/marines probably have a few pieces of the puzzle as well.

  • But it's odd that very few stories exist. If you believe the Bink's Sake theory posited by Artur and a few others, this seems to be the only story that's survived "in full".

We have seen a fruit that can literally (almost) erase someone from history. Sugar. With just a touch, all memories of a person are removed from the entire world's population.

Oda went through painstaking detail to show us just how devastating this ability is. Doflamingo goes through a lot of trouble to keep Sugar safe from any and all harm, one of his chief officers is explicitly assigned as her bodyguard.

• As a sidenote, Doffy also says "he knows the treasure they're hiding in Mary Geoise". It could be related.

We also saw several officers of Doffy using upgraded versions of fruits we've seen in the past: Kilo Kilo (Miss Valentine) vs. Ton Ton (Machvise). Bomu Bomu (Mr. 5) vs. Pamu Pamu (Gladius) . Interestingly enough Oda chose to upgrade Mr. 5's and Miss Valentine's fruits, who were both partners in Baroque Works (and there are a lot of BW vs. Dressrosa obvious parallels).

Guess what else the Hobi Hobi no mi does? It grants the user eternal youth. Sugar is 22 years old. She's owned the fruit for 12 years, and looks 10 years old.

My theory is that Imu has an upgraded version of Sugar's Hobi Hobi no mi. And s/he has awakened it. Imu has lived for centuries and centuries with eternal youth. And through awakening Imu is able to literally erase things from history.

Except the poneglyphs, because they are indestructible, and likely made of a devil-fruit resistant material. What if they are imbued with haki? Note that armament haki is portrayed as black, while advanced armament is portrayed as red. Could be a coincidence, but it's a strange one.

What if the Kozuki Craftsmen who created the Poneglyphs literally poured their haki into these stones? Turning them into the equivalent of a "black blade", but instead just as a way to preserve the history they somehow knew was being erased?

We know that Haki can resist the effects of a devil fruit, as Law was unable to truly affect the Yonko because their haki was too strong.

A few sidenotes:

(Ch. 1037 spoilers) -> No I do not think that "the fruit" is Sugar's fruit. It makes no sense given all the context.

Do the Straw Hats still remember that Vivi exists? What about Sabo? Cobra? Food for thought. Rebecca and Vivi share a lot of parallels, I wonder if Cobra has been "removed from history" as Kyros was.

Furthermore, since Sugar can issue orders to her toys, Imu would be able to do the same. You think Tama's fruit is insanely overpowered? We forget that Sugar turned half the Tontatta into toys and ordered them to attack their comrades, who had no memory of them anymore, and they had no choice but to do so.

What would an "upgraded" version of this do? Change the WILL (a central theme of the story) of the person? A bastardization of Sugar and Tama's fruit?

Still not convinced? Look what Sugar is wearing on her head.

Look familiar?

TL;DR:

Imu has an upgraded version of Sugar's fruit. This gives him/her eternal youth, and the ability to literally erase/extinguish things from history. Perhaps physically as well, and likely not restricted to living beings like Sugar's is. And if awakened, perhaps even 'at a distance' rather than requiring touch like Sugar's does.

The Poneglyphs are able to resist this effect because they have been imbued with the Kozuki clan's haki.