Seastone is a naturally-occurring but immensely rare mineral best known for its negation of Devil Fruit abilities.
Though it originates from Wano Country,[2] Seastone is currently utilized in many inventions and devices across the world. As the most advanced research on it was conducted by the Marine scientist Dr. Vegapunk, its use is particularly common among the Marines and the World Government.[3]
We still don't understand all the properties of Seastone, but we do know that it emits an energy identical to the ocean's. Think of it as the sea in solid form.
According to Pagaya, one of Seastone's main components is Pyrobloin (パイロブロイン,Pairoburoin?, Funimation: Pyrobroine), a type of "corneous particle" (角質の粒子,Kakushitsu no ryūshi?) dense enough to form both Sea and Island Clouds upon absorbing enough atmospheric moisture.[5] Consequently, a solid mass of Seastone—in addition to holding several of the sea's metaphysical properties—is as hard as diamond.[6]
What Seastone looks like in its raw, unprocessed state remains unknown, though most if not all of its byproducts tend to be a dark gray color.
Because Seastone so strongly resembles the sea itself, Sea Kings cannot distinguish the two. By layering the bottom of ships with Seastone, creatures that are underneath the ship will be unaware of the vessel's presence, and thus will not attack it.[3] However, while the Seastone hides the movements of the vessel while it is traversing above the Sea Kings, that does not mean they cannot see the ship itself; if a Sea King comes to the water's surface, then it will be able to perceive the part of the ship that isn't protected by Seastone.[7]
Effects on Devil Fruit Users[]
Smoker using Seastone to incapacitate Luffy.
Coming into contact with Seastone has the same effect on a Devil Fruit user as falling into the sea, it will drain the Devil Fruit user of their stamina and nullify their powers, the only difference is that lack of the risk of drowning. This weakening effect only works upon direct and constant physical contact with the Devil Fruit user in question, as the effect stops immediately once the Devil Fruit user is no longer in contact with the substance.[8]
Seastone can be modified to make a Devil Fruit user weak to only a certain extent; for example, Seastone handcuffs are generally modified to rob a prisoner of their powers, but still leave the prisoner strong enough to walk normally, and in some cases, perform hard labor.[9][10] The degree of "weakness" induced by the Seastone depends on its density and composition, with 100% pure Seastone having the greatest weakening effect on Devil Fruit users.[11] However, a Devil Fruit user can resist and even ignore the weakening effect if they have enough physical endurance.[12]
It has been suggested that being weakened by Seastone affects a Devil Fruit user's ability to use Haki, as Luffy was unable to use it with Seastone handcuffs on and became able to use it once again they were removed.[13] It is unknown whether Seastone affects Haki users without Devil Fruit abilities this way.
Although a Devil Fruit user loses their powers when in contact with Seastone, said powers can still be used on and affect Seastone, as long as the user themself is not making contact with the substance. Examples include Mr. 3 using his candle wax to create a key that can unlock Seastone cuffs and cell doors,[14][15]Trafalgar Law using spatial manipulation to switch Seastone chains with regular ones and cutting through other Seastone chains,[16] and Shikilevitating battleships in Marineford despite the hulls being lined with Seastone.
Items[]
Because Seastone is as strong as diamond and is such an effective countermeasure against Devil Fruit users, it is often used by various organizations to make a variety of weapons, such as blades or bullets, and restraints, such as shackles or cages.
Some of these items are adapted so that people with Devil Fruits can use them without actually making contact with the Seastone itself, a circumstance which would nullify their own powers in the process of trying to handle another Devil Fruit user.[8]
Wano Country has many craftsmen who have expertise in working with the mineral, and are the only ones skilled enough to forge it into delicate items, such as nails.[2]
Weapons[]
Nanashaku Jitte: Smoker's jitte, which has a tip is made of Seastone so Smoker can use it to nullify his opponent's Devil Fruit powers.[8]
Lipstick: Stussy carries a piece of Seastone hidden in a tube of lipstick which she used to weaken Rob Lucci before biting him and rendering him unconscious.[21]
Non-Canon[]
Z's Seastone Battle Smasher arm.
Battle Smasher: Z's large mechanical prosthetic arm has Seastone embedded in it, allowing him to use it to efficiently defeat enemies with Devil Fruit powers. In addition to being a strong bludgeoning weapon, it was large enough to actually hold a full-grown normal sized human, effectively sealing their powers and restraining them in one move. Being made of Seastone, the device is also virtually as hard as diamonds, thus providing an excellent defense.[22]
Bullets: Z uses them for long-ranged attacks against Devil Fruit users, such as Monkey D. Luffy. Those bullets not only wound Devil Fruit users, but also rob them of their strength and their ability to use their powers until they are extracted, making them very effective weapons.[22]
While Capone Bege threatened to shoot down Caesar Clown with Seastone bullets if he did not show himself, Bege revealed that he did not have such bullets, leaving it unknown whether or not they exist in canon.[19]
Restraints[]
Prison Bullets (監獄弾,Kangoku Dan?): Prison Bullets are nets made of Seastone which were designed by the Marines to capture Devil Fruit users. They were first used in Loguetown by Marines to nullify Buggy and Alvida's powers after Smoker apprehended them. In the anime, these are shown being fired out of bazookas.[1] A much larger net was used to capture Luffy, Buggy, and Mr. 3 in Impel Down, but a Sphinx captured with them tore it apart, indicating that only parts of the net contain Seastone, while the rest is steel cable.[23] They were later seen being fired out of bazookas to capture escaping prisoners by Impel Down's Prison Bullet Bazooka Unit.[24] They are called Jail Bullets in the Odex dub and Cage Shots by Funimation during the Loguetown Arc.
Seastone cage.
Seastone Cage: Seen in the Arabasta Kingdom, it was used by Crocodile to drain Luffy and Smoker's powers and make them unable to use their Devil Fruit abilities. Interestingly, while they were only physically weakened if they actually touched the bars, it appears that just being in the cage robbed them of their powers, as Smoker seemed unable to simply break his Logia body apart and send the pieces through the bars to reconstitute on the other side. The World Government's central prison, Impel Down, also uses Seastone cages.[8]
Seastone Cuffs: Special handcuffs made to arrest those with Devil Fruit powers. The lock is made of Seastone so that when a Devil Fruit user is wearing them, they cannot use their powers, but unlike other Seastone, it does not inhibit their mobility. During the Enies Lobby raid, Nico Robin wore them until Sogeking delivered the key to the bridge. Despite being unable to use her powers to fight back, she was able to move, and could attempt to escape or otherwise resist being taken to the Gates of Justice.[6] Sogeking tried to throw Seastone handcuffs at Jabra and Kaku in order to prevent them from using their Devil Fruit powers and make them easier to defeat, but got distracted by Kaku's "square" giraffe face and accidentally threw them on Zoro's wrist, and got handcuffed to him while also ducking due to Kaku's Amanedachi.[25] These were also hooked onto Ace's arms and legs in his prison cell in Impel Down to prevent him from using his Devil Fruit powers. Boa Hancock was required to wear one while visiting Ace at Impel Down. Onigumo also clasped one onto Marco during the Summit War of Marineford, to nullify his Devil Fruit powers.[26]Usopp fired a pair of Seastone shackles to coil around Caesar Clown's neck, disabling his Gasu Gasu no Mi ability.[27]
Seastone Chains: Caesar had several Seastone chains on Punk Hazard, however, Law replaced some of them with regular ones. The chains were used to bind Law, Luffy, Smoker, and the rest of their party in a cage to be used to show Shinokuni's power.[16] The Prisoner Mine in Udon has access to 100% pure Seastone chains. They were used by Queen's subordinates to restrain Big Mom after she fell asleep.[28]
Other Uses[]
A sea king passing by peacefully under a ship with Seastone cover.
Marine Ships: Dr. Vegapunk has discovered that Seastone can mask the presence of a ship from Sea Kings and other sea-dwellers, and therefore had the bottom of Marine ships covered in a layer of it, which is especially useful when traveling across the Calm Belt.[3] However, the Sea Kings can still see the ship, so it is not an absolute protection.[7]
Jewelry: Nico Robin was weakened by a Seastone necklace in a filler episode when she tried to stop Ian from escaping the Rainbow Mist.[29]
Fortification: Some people use Seastone to fortify sensitive buildings and facilities, making them virtually indestructible. The SMILE Factory in Dressrosa was made out of Seastone.[30]
Translation and Dub Issues[]
While Seastone is used almost universally among English-speaking fans, it technically abridges the original term Kairōseki (海楼石?), by excluding the rō (楼?) character between the "sea" (海,Kai?) and "stone" (石,Seki?) characters. This rō may be variously translated as "storey", "building", or "tower"; its particular significance to the material, if any, is yet unclear.
↑ 7.07.1One Piece Manga and Anime — Vol. 53Chapter 516 and Episode 410, The Kuja pirates spot a dead Sea King and Momonga notes though they can move above the Sea Kings nest unnoticed, it does not hide them from the creatures' sight.
↑One Piece Manga and Anime — Vol. 93Chapter 935 (p. 6) and Episode 930, An Udon prison guard mentions how their prisoners with Devil Fruit powers are restrained with just enough seastone to allow them to perform manual labor.
↑One Piece Manga and Anime — Vol. 94Chapter 951 (p. 12-14) and Episode 952, Big Mom continues to act normally, despite being wrapped in 100% pure Seastone chains.
↑ 16.016.1One Piece Manga and Anime — Vol. 68Chapter 677 (p. 10) and Episode 603, Law explains how he has replaced the Seastone chain with an ordinary one.
↑One Piece Manga and Anime — Vol. 28Chapter 260 and Episode 171, Wyper uses his Seastone equipped skates to stop Luffy's attacks.
↑One Piece Manga and Anime — Vol. 29Chapter 275 and Episode 180, Wyper uses his Seastone equipped skates to hold Enel down.
