The Rain God and the Deep Deep Sea
The central claim of this theory is that the Yami Yami no Mi is not a logia of darkness at all.
It is a Mythical Zoan: Hito Hito no Mi, Model: Zaza—the Rain God Fruit.
What the world has long interpreted as the devil fruit of "darkness" is in truth the manifestation of the deepest sea, the irresistable and inescapable darkness of the bottom of the sea.

In our world, more commonly known as Davy Jones' Locker.

Why Not Dragon — And Why Nika Still Fits
The first reaction I expect is, that you assume that the fruit of Zaza should belong to Dragon, because we expect great things from him and he is already connected to weather phenomena, like heavy wind, rain and potentially thunder (logue town). Your

Okay, so I want to thank anyone who takes the time to read this theory. I’ve had this idea for some time now, with that being said I’ve never felt like I had the proper medium to share it in detail. Thank you to Morj for building the space.

Now on to the theory:

I think the One Piece is the group of people who lived in the Ancient Kingdom that Joyboy wanted to save, when he sent them forward in time with Lady Toki’s power he left behind stone tablets to ensure someone would be there to meet them. And I think the note Roger read in Laugh Tale was something along the lines of “Hope you made it there in One Piece!”

“We eventually realize that there once existed another country, nothing remains of it.” (Clover Ch. 395 Page 7) Over 800 years ago there

What really happened during the Void Century, and why was the world forced to forget it?

For 800 years, the World Government has gone to extraordinary lengths to keep one period of history hidden.

The Void Century.

It isn’t just that the history was forgotten. It was deliberately erased. Ohara was destroyed for studying it. The Poneglyphs were forbidden. The Ancient Kingdom disappeared from the historical record. Even the Will of D, carried by people descended from the enemies of the World Government, became something the Government wanted erased.

That raises a more important question than simply asking who won the war.

What happened during the Void Century that made the truth so dangerous?