Poseidon
The power to command the ocean's greatest giants lies within a single voice.
Poseidon is not a physical weapon or a mere title, but one of the three Ancient Weapons capable of commanding the Sea Kings, colossal beasts that dwell in the deepest trenches of the world's oceans. Unlike the other weapons which rely on destructive firepower, Poseidon represents the power to communicate with and control these leviathans, granting its possessor—the Mermaid Princess herself—the ability to summon an army of giants or command them to crush ships and islands instantly.
In the lore of the One Piece world, this power has been prophesied for eight hundred years as a force that could either bring about the end of the world or facilitate the opening of the final route. The title is passed down through bloodlines rather than being an object one can pick up, making its current bearer a figure of immense strategic importance to both the World Government and those seeking to uncover the secrets of the Void Century.
- Type
- Ancient Weapon (Spirit/Ability)
- Primary Ability
- Communication with Sea Kings
- Current Bearer
- Princess Shirahoshi
- Lineage
- Descendant of the Merfolk Royal Family
- First Appearance
- Fish-Man Island Arc
- Status
- Active and Awakened
Lore & Background
The legend of Poseidon dates back eight centuries to the era of Joy Boy, who was not the possessor of this power but an ally who made a solemn promise to the Mermaid Princess of that time. At that time, the weapon was defined as a living person: a mermaid princess named Poseidon, whose descendants inherited the name and the power through generations. The World Government has long feared this specific Ancient Weapon because its potential to control Sea Kings could easily dismantle their naval dominance or destroy the Red Line itself if used aggressively.
For centuries, the title passed silently within the Merfolk Royal Family of Fish-Man Island, hidden from the world until the arrival of the Straw Hat Pirates. The power remained dormant and terrifyingly misunderstood by the current princess, who believed herself cursed for her inability to control the beasts. It was only through the encouragement of Luffy and the revelation of her true heritage that she realized her voice could summon an army capable of reshaping the map of the world.
The significance of Poseidon is inextricably linked to the Other Ancient Weapons, Pluton and Uranus. The prophecies suggest that when all three are united or activated simultaneously, they can either destroy the Red Line to connect all oceans or reveal the path to Laugh Tale. While Pluton represents a warship of mass destruction, Poseidon offers a living, breathing force of nature that answers only to the will of its master.
In Their Own Story
The ocean floor trembled, not from an earthquake, but from the rhythmic thrumming of massive hearts rising from the abyss. Above the dark waters, the air grew heavy with salt and dread as shadows eclipsed the sun. A young mermaid princess stood trembling on the deck of a ship, her voice cracking under the weight of centuries of fear. She closed her eyes and spoke not to humans, but to the deep.
"Please... help us," she whispered.
Instantly, the water around them began to boil as thousands of scales broke the surface. The Sea Kings, once mindless predators of the deep, turned their massive heads with gentle curiosity toward her voice. Their eyes, vast and ancient, locked onto the small figure before them. With a single command from her lips, the giants bowed in unison, creating a bridge of flesh and scale that stretched across the horizon, ready to carry the dreams of the living into the unknown.
Reader's Guide
Poseidon functions as a unique form of Haki-like communication specifically attuned to Sea Kings. Unlike standard commands which these creatures ignore, the bearer of Poseidon can issue direct orders that are obeyed instantly and without question. This ability allows for both defensive maneuvers, such as creating barriers with the bodies of the beasts, and offensive strikes capable of leveling fleets or islands.
The power is innate to the bloodline of the Merfolk Royal Family but requires emotional maturity and confidence to activate fully. In its dormant state, the bearer may hear the voices of Sea Kings but cannot control them, often perceiving this as a curse. Awakening the power involves overcoming fear and accepting one's destiny, at which point the connection becomes absolute.
Currently, Princess Shirahoshi is the sole known wielder. She does not need to physically touch or be near the beasts; her voice carries across vast distances of water. The World Government seeks to capture or eliminate her to prevent her from joining forces with the other Ancient Weapons, making her a primary target for the Marines and Blackbeard's crew alike.
Did You Know?
- The name 'Poseidon' is passed down through generations; it was the name of the mermaid princess eight hundred years ago who made a promise with Joy Boy, rather than Joy Boy possessing the power himself.
- Sea Kings are generally hostile to humans, but they instantly recognize and obey the voice of Poseidon without any need for training or coercion.
- The ability to control Sea Kings is considered a threat so great that the World Government has kept the existence of the current bearer secret from the public for centuries.
- Unlike Pluton (a ship) or Uranus (unknown), Poseidon is canonically defined as a living person whose power is tied directly to their emotional state and willpower.