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The Petrification Device ( (せき) () (そう) () Sekika Souchi), also known as the Petrification Weapon ( (せき) () () () Sekika Buki), or the Medusa (石化武器 (メデューサ) Medyūsa), is a technological device that can cause petrification and was used as a weapon by Kirisame and Ibara.

At some point a few centuries prior to the current story's events, several of these devices fell from the sky above Treasure Island, whose inhabitants began abusing its power. During the South America Arc, it is revealed that there is a pyramid of petrification weapons laying at the site of the original petrification event. The device can be also used as stealth material.


Senku holding the petrification device.

The petrification device is a small, metallic-looking object with a smooth surface in the shape of a trefoil knot with only one side, similar to a möbius strip. It appears to be approximately 6cm (2.5 inches) across at the widest point. It has tiny etchings all over it, possibly indicating extremely delicate and futuristic internal hardware. The one found on Treasure Island has a thin thread attached to one of the loops for ease of recovery. It also doesn't show up on radar.[1]

Senku notes several things about its form:[2]

  • Smooth surface.
  • Circuitry inside.
  • Translucent with photosphere.
  • Twisted shape like Möbius strip.
  • About a particular element of the device:
    • Resembles LED light in form.
    • Big range of light output.

Later, Joel discovers that the device has a central core made of diamond.[3] A diamond can only be used if it does not have any fractures,[4] and the cleavage planes run vertically and intersect at the tip, allowing the diamond to be split perfectly down the middle.[5] The diamond gets blackened with usage.[6]


The medusa's petri-beam.

In order to activate the device, a distance must be stated followed by a timing. The distance used is the maximum radius of the sphere of light, which must be in metres, and the time delay to activation in seconds or minutes. It then makes a 'whoom' (ブウウン) noise and glows, presumably to confirm that it's active. It can also be activated using a microphone and speaker combination.[7] The voice command must be completed fully with no letters omitted otherwise the device will not activate (so saying "10 secs" would probably not work).[8] It is unknown if other units of measurement may be used, or if the command can be inverted. Fractions of distances or timings have also not been attempted yet.

The medusa activating and making a noise.

Once activated, the device makes a 'k-chk' sound then emits a flash of light dubbed the 'petri-beam' that expands radially at a constant speed.[9] Anything touched by the light will start to become petrified. The beam itself does not expand at the speed of light, and is possible to dodge if one moves quickly enough.[10] Being in the shadow of the light also does not stop the beam, as it seems to wrap around any objects within the area regardless.[11] It is unknown if the expansion speed is proportional to the magnitude of the radius or if the slower speed is simply due to the power source depleting.

When thrown and activated, the device stays fixed in space while releasing the beam, relative to the Earth as it doesn't go shooting off due to the Earth's rotation. The device also runs on some sort of limited energy source, (later revealed to be diamonds) as the accuracy of its total radius decreased after Ibara petrified the whole island.[12] The largest known radius attempted is 12,800,000 metres, the diameter of the Earth.

As Ukyo's statement, Medusa can be also utilized as a radar-absorbant hull, allowing Senku and his gang acquire a stealth ship by coating their hull with Medusa's fragments. When testing Medusa's radar absorbant capabilities in close range, neither Ukyo nor Leonard were able to pick anything off the radar, indicating Medusa was suitable not only as a weapon, but also as defense and stealth material. Because of this, the science group were able to create a stealth ship.



The petrification devices falling from the sky over Treasure Island centuries ago.

Matsukaze tells the Kingdom of Science what happened during his time a few centuries back. A great number of petrification devices rained down from the sky above the island.[13] Either from hearing the voice that seemed to accompany the devices or from trial and error, the inhabitants of Treasure Island figured out how to use them. Matsukaze's master realized that if the devices were allowed to be wielded, chaos would reign. As such, he ordered his men to find and destroy them.

The petrification device being used on a younger Amaryllis and her friends.

With only one remaining, Matsukaze's master lay dying from a fatal injury, questioning why many were sent rather than only one big one. Matsukaze is petrified shortly afterwards, stating that only one device remains despite several being shown in the background. The image he carves onto himself does not appear to match the shown medusas very well, however he vows to tell future generations of their danger.[14] This final device is presumably the one Ibara uses later.

Later, in the year 5736, five years prior to Senku arriving on the island, the petrification device was used by Kirisame and Moz against Amaryllis and her four friends to prevent them from fleeing the island.[11]

Treasure Island Arc

In the year 5741, Kirisame continued to use this as a weapon. When the Kingdom of Science arrived with the Perseus on the shores of Treasure Island, Kirisame used it to petrify the majority of the crew, with the exception of Senku, Gen, Soyuz and Kohaku who were exploring, Suika who got kicked away by Ryusui and Ginro who was swimming at the time.[15]

Kirisame throwing the medusa at Ginro and Kohaku.

Ibara later orders Kirisame to use it again against Kohaku and Ginro after Kohaku started yelling about the truth of the state of the master of the Petrification Kingdom to try and shut her up. Kohaku's goal was trying to get Kirisame to use the device on her and Ginro, who got fatally stabbed, to save him. The inhabitants are also asked to shield their eyes "or else be turned to stone", presumably a measure to hide the existence of the device from them[16]

Under Ibara's orders, Kirisame throws a fake petrification device during the first battle at Wavebreak Cliff to test Mozu's loyalty. Ibara kept the real device for himself, escaping to the Perseus.[17]

The device immediately after activation.

Ibara then asks Oarashi to run the device to the center of the island, hoping to petrify all of the remaining invaders in one go. Kirisame argues with him, saying that not all of the islanders have finished evacuating yet and that the master told her that the device was never meant to be used over a large area. Realizing Kirisame is no longer on his side, Ibara petrifies her. Yo then shoots his hand, causing him to drop it into the ocean.[18]

Yo retrieves the device from the ocean but doesn't know how to use it. Ibara jumps in after him and activates it while Yo was holding it, petrifying him.[19] Oarashi dives overboard as well, and Ibara takes the opportunity to use him to petrify the whole island. He sets it for fifteen minutes, allowing Oarashi enough time to get to the middle of the island. The team realizes what's happened and Taiju tells everyone that Oarashi has the device and that he needs to be stopped. The islanders, confused as they don't know about the device, think that they need to protect him instead. It's revealed that Ibara forced Oarashi to swallow it, and with no means to stop it in time, the island gets petrified.[9]

The medusa after being used in Yo's hands

Ibara smashes Oarashi's body to retrieve the device from his stomach. He then finds the mobile lab, wherein Senku tries to use a microphone to activate it.[20] The speaker is too far away for it to work, however Ibara throws it away from himself regardless. Senku snatches it up and tries to petrify Ibara, but his command is interrupted and thus doesn't activate it. Ibara grabs it back and chases Senku to Wavebreak Cliff, where he attempts to use it against Senku once more. Ryusui, freshly revived, uses the drone to snag it midair.[21] A tug-of-war happens between the two sides, resulting in the device petrifying Ryusui as he attaches the earpiece. Senku then immediately afterward petrified Ibara after using the speaker.[7]

Why-man then attempts to set the device off at a radius of 12,800,000 meters (the diameter of the Earth) using the radio, but fails.[22]

New America City Arc

Once depetrified, Matsukaze revealed that during his time, several petrification devices fell from the sky all across the island.[13]

After returning to Ishigami Village, Senku reports that the weapon is almost depleted of power, as the last time he used it the radius did not reach the correct maximum and fell short. He uses the device's remaining power, which just barely flickers, to petrify Tsukasa and save his life.[12]

On the way to America, Matsukaze continues his story of the petrification weapons. He says that he's unsure how the people managed to figure out how they work, only that they started using them soon after. Him and his master found and destroyed almost all of them, bar one.[14]

The device falling into the river after Stanley shoots it.

Finding out that Dr. Xeno is their opponent, Senku realizes he can pretend to have super science weapons to trick Xeno into surrendering, as long as they don't reveal that it's out of power.[23] Ukyo later delivers it to the American Colony's front door via arrow. Xeno sees it and realizes it's hyper-tech, leaving Gen to explain what it is and bluff that the Kingdom have more of them. Stanley decides he's not particularly scared of that fact, as they have a submarine they can use to take over the Perseus before anyone can activate the device.[24]

With Xeno captured, Stanley ties the petrification device to the prow of the ship. The members remaining on the captured Perseus pretend to be scared, causing enough of a diversion to allow the smaller ship to escape. Before it passes, however, Stanley shoots it several times, launching it high into the air above the ship.[25]

South America Arc

Sometime later, Homura Momiji free dives into the river, retrieving the device that sunk to the bottom. Bringing it to the American Colony, Nikki then discusses tinkering with the device so it can be used for healing any injured or sick people in the future. Internally, Nikki is aware Senku has a use for the device and cannot let the truth slip. Brody agrees, but thinks the timing of the request is suspicious and insists any fiddling they do with it is monitored. It's revealed that the members of the Kingdom of Science left in North America don't know they're heading for the source, hoping to find the original device. As they are unfamiliar with performing a proper diagnosis, they revived watchmaker Joel. Getting to work, Joel notes several things about the weapon: Joel was fascinated by its mechanics and described the circuitry is glass or mineral-like, and the core is a diamond.

The pyramid of petrification.

Theorizing a way to get it functioning, he removes and reinstalls the diamond. Wanting to confirm it, Joel tests it on himself and gets petrified in the process.[26]

After a long trek through the Amazon rainforest, Senku and his allies discover a huge stepped pyramid of the devices.[27]

Once the diamond was re-created, Joel said the device was functional. At that point Dr. Brody and his soldiers immediately confiscated the device having become suspicious of the intentions of the Kingdom of Science. This resulted in a brawl for the device. Despite Dr. Brody's attempt to lock the device away, Joel was still able to activate it using Why-man's regularly timed broadcast, triggering the second global scale Petrification Event.

New Stone World Arc

7 years later, the members of the Kingdom of Science were finally revived, thanks in large part to Suika's efforts. Even Hyoga, who was stated by Tsukasa to have lost his life prior to the petrification, was successfully brought back. Tsukasa relayed this information to Senku, and through this, the latter's hypothesis was confirmed. That it's possible for the petrification device to even nullify death. With this, humanity has secured a means of immortality.[28]


  • One of the nicknames for the device, the Medusa, is a reference to one of the Gorgons from Greek mythology.
  • The device has a finite amount of power, another nod to the formula E=MC2.
  • Once a command has been issued, it doesn't appear to be possible to override or stop it in any way.
  • The voice command must originate fairly close to the device in order to verbally activate it, simply being within hearing range does not work.
  • It was mentioned a voice was heard with the devices falling, it is unknown if it is connected to the mysterious creator or Why-man.[29]
  • Matsukaze said that they were able to destroy the devices, however Stanley is shown shooting it several times, making it unclear how durable the devices are and how difficult they are to break.[25]
  • The voice used to activate it may not have to be someone real, as Why-man uses a synthetic version of Senku's voice to try activating it.


  1. Dr. Stone Manga: Chapter 181, Page 17
  2. Dr. Stone Manga: Chapter 139, Page 5
  3. Dr. Stone Manga: Chapter 177, Page 15
  4. Dr. Stone Manga: Chapter 182, Page 7
  5. Dr. Stone Manga: Chapter 185, Page 8
  6. Dr. Stone Manga: Chapter 182, Page 3
  7. 7.0 7.1 Dr. Stone Manga: Chapter 137
  8. Dr. Stone Manga: Chapter 136, Page 3
  9. 9.0 9.1 Dr. Stone Manga: Chapter 133
  10. Dr. Stone Manga: Chapter 135
  11. 11.0 11.1 Dr. Stone Manga: Chapter 106
  12. 12.0 12.1 Dr. Stone Manga: Chapter 141
  13. 13.0 13.1 Dr. Stone Manga: Chapter 139
  14. 14.0 14.1 Dr. Stone Manga: Chapter 146
  15. Dr. Stone Manga: Chapter 103
  16. Dr. Stone Manga: Chapter 121
  17. Dr. Stone Manga: Chapter 127
  18. Dr. Stone Manga: Chapter 131
  19. Dr. Stone Manga: Chapter 132
  20. Dr. Stone Manga: Chapter 134
  21. Dr. Stone Manga: Chapter 136
  22. Dr. Stone Manga: Chapter 138
  23. Dr. Stone Manga: Chapter 158
  24. Dr. Stone Manga: Chapter 161
  25. 25.0 25.1 Dr. Stone Manga: Chapter 169
  26. Dr. Stone Manga: Chapter 177
  27. Dr. Stone Manga: Chapter 180
  28. Dr. Stone Manga: Chapter 197
  29. Dr. Stone Manga: Chapter 146, Page 7

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