Item from One Piece by Eiichiro Oda
A rare mineral that emits the same energy wavelength as the sea itself. Contact with Seastone nullifies Devil Fruit powers completely and drains the user's strength. The Marines' primary tool for containing Devil Fruit users.
Seastone is the great equalizer in a world of Devil Fruit superpowers. No matter how powerful a fruit — whether it grants rubber bodies, magma control, or the ability to destroy the world with earthquakes — Seastone contact neutralizes it completely. The Marines coat their warship hulls in Seastone to pass through the Calm Belts undetected by Sea Kings. Seastone handcuffs are standard issue for capturing Devil Fruit pirates. Smoker tipped his weapon with it to strike Logia users. The stone's origins are mysterious — it occurs naturally but its properties suggest a connection to the sea itself that science hasn't fully explained. Wano's master artisans are the only people who can work Seastone into fine applications, which is one reason the World Government was interested in controlling Wano's resources.
A dense, dark-colored stone with a slightly blue-grey sheen. Can be worked into various forms: handcuffs, cage bars, weapon tips, ship hull coatings, prison cells. Wano Country has the most advanced Seastone craftsmanship in the world — their artisans can work it thin enough to embed in weapon edges and nail tips. To a Devil Fruit user, touching Seastone feels like being submerged in the ocean: immediate weakness, power nullification, and if they're a Logia, their intangibility fails completely.
Also known as: Seastone, Sea Prism Stone, Kairoseki