Forty years ago, Blackbeard was born. That much we know. But what was happening around then? Well the Rocks Pirates crew was in full swing, had gathered up nearly every powerful pirate they could get their hands on, and were running a massive operation from the Pirate Paradise island. Rocks D. Xebec had it made. He even possibly had made time to start a small family.
So far, things line up just fine. Blackbeard is born, Rocks D. Xebec is nearly the most powerful pirate in the world, and just two years later he faces defeat at the hands of Garp and Roger.
Rocks D. Xebec more than likely dies in this moment. But just like Brook after his solo, he doesn’t die. Rocks could’ve been in possession of a fruit that halted that process, but does not send him back to his own body. You see, Rocks D. Xebec had eaten the Sere Sere no Mi(or some similar name) which would let him possess another man’s body, but only if he had already perished.
Lightning round. Rocks D. Xebec possesses his son, Marshall D. Teach. Blackbeard has two entities inside of him. This is the origin of his Atypical body, why Luffy and Zoro knew that Blackbeard wasn’t just Blackbeard. The Sere Sere no Mi respawned in the wild, or possibly was lost on God Valley, thus the two souls can technically both carry a fruit (Not sure how this helps blackbeard’s third fruit theories).
This explains Blackbeard and his often conflicting personalities. Sometimes he is very courageous and confident, and others he can seem very stupid, and cowardly. These changes are at the drop of a hat. The brave aspect is most likely Rocks shining through. This explains a lot of Blackbeard’s knowledge on Devil Fruits, and his instant expertise with the Gura Gura no mi.
*Theory by nixiera
