Introduced for the very first time in One Piece's Alabasta arc, the Pluton was revealed to be an Ancient Weapon with powers of mass destruction. It played a massive role during the pre-time skip of One Piece in both the Alabasta and the Water 7 sagas. Mentioned first by none other than the former Shichibukai, Crocodile, and the Alabasta arc, the Pluton was revealed to be a massively powerful weapon capable of wiping out entire islands with a single shot. With its powers, Crocodile planned to take over the entire world and become a major force in the New World. Unfortunately for him, Robin did not reveal the location of the weapon and he ended up being defeated by Luffy.
The Water 7 arc, once again, revolved around the Pluton as the main plot point. The ship itself was built on the island at some point during the Void Century. Since then, the blueprints for the Pluton had been passed down from generation to generation and, eventually, they ended up with Franky. Robin and Franky were both central to the storyline of the Pluton before the timeskip and their connection to the weapon was, obviously not going to stop there. With the location of the Pluton being unknown, it was inevitable for it to come up at some point in the story. In One Piece's previous chapter, Nico Robin finally revealed that the weapon was in Wano Country itself.
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The Ancient Weapons are described to be tools of mass destruction that existed during the Void Century. Each one of them is known to be capable of destroying the entire world if let loose. Their names are derived from those of Greek gods and they include Pluton, Poseidon, and Uranus. Although most information about Uranus remains to be largely
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