One of the big mysteries of One Piece is just how Blackbeard is able to use multiple Devil Fruit powers when that should theoretically kill any being. I don’t have any strong theories as to what the truth is, but I do know one thing: when we do discover the secret, I think it’ll be one of the most satisfying moments in the entire series.
I love that trope, I really do. Whether it’s Sauron realizing that the One Ring is steps away from Mount Doom, and is filled with terror, or Voldemort coming to the horrifying realization that his Hocruxes are being eliminated, one of my favorite moments in fiction is when a villain realizes that their special hidden achilles heel, and thus they themselves have been exposed.
If I were to say why I’m so fond of this idea, I’d say that it comes partially from how it resembles “boss fight” sensibility. Of course, this sort of storytelling element predates video games by a significant margin, but it is arguably most straightforward in the context of games. Only the worst weapon can harm Dr. Wily. Lavos Core attempts to fool enemies by hiding its true self in a seemingly unimportant floating “pod.” This idea can even extend to something like Gradius, where the final boss is a weaponless and disembodied brain. Here, the idea is that your final adversary is defenseless precisely to imply that you were never “supposed” to reach it—the soft, squishy point behind layers and layers of minions and firepower was meant to be unassailable.
But that puzzle aspect is only one component, and what really makes it satisfying is that the moment of unwanted revelation about their weakness being exposed is predicated on a contradiction. Villains like Voldemort and Sauron want to be invincible, but by pursuing that goal, they inadvertently create the cracks in their own armor. Voldemort fears death above all else, so he tries to achieve immortality by placing pieces of his soul into other objects and hiding them away, which in turn makes those very items a source of obsession for Voldemort. Sauron is already immortal, but his desire to control and dominate everything results in his transferring most of his power into the One Ring. Even when he first loses the One Ring in combat, the fact that it’s near-impervious gives Sauron a certain reassurance. He will eventually reunite with the ring because nothing is strong enough to get into Mordor if it’s not on Sauron’s terms. They use both smoke and mirrors and sheer martial strength to try and hide these flaws, so to see their best-laid plans begin to crumble gives me joy.
It’s precisely because Blackbeard goes to such great lengths to hide the workings of his multiple-Devil-Fruit usage that makes me confident that the reveal (and the ultimate use of it against Blackbeard) will be one of the best plot threads to come out of One Piece. His obsession with power, and the weak-minded truth of his being provide a perfect formula for this trope to play out in the best way possible.