|This article is about a/an object and major plot element in Kamen Rider Build.|
Discovery and Activation
The alien artifact was found by Soichi Isurugi, who was a crew member of the INSET exploration vessel Prominence during the astronaut's survey of Martian caverns at the time. Upon being touched, it reacted to the human by shedding its stone encasing to reveal its true form. The box was then carried back onto the Prominence and back to Earth. The Pandora Box was believed to have been technology from part of an advanced civilization on Mars.
During the ceremony celebrating the return of the Mars expedition ten years ago, the Pandora Box was put on display, when Soichi dashed forward and touched the box, activating the box's mysterious powers. A bright flash of light emanated from the box, as it generated the Skywalls which divided Japan into three sections. The box also somehow changed the behaviour of everyone present at the ceremony, invoking aggressive tendencies within their behaviour. As a result, the country itself was torn apart into three districts, each with their own capital and government and pursuing different aims: Hokuto, focusing on social welfare; Seito, focusing on economic recovery; and Touto, focusing on traditional pacifism. The Pandora Box is currently kept in a vault in the Touto Institute of Advanced Matter Physics, where it is being studied so as to find a possible way to resolve the Skywall crisis.
Sento investigated the Disaster using footage from that day and used a light filter software program to discover that the Pandora Box changed colors and jettisoned two of its green panels upon activation, yet retained its shape. This means that the Pandora Box consists of multiple layers of panels that are interlocked to form its shape, yet somehow can retain its same form and size. Director Himuro confirmed to Sento that the Pandora Box has at least two layers in its structure and the green panels that came loose were stolen three years ago. He suspected that either the government of Seito or Hokuto were involved in the theft and the prime suspect is the astronaut who activated the device.
As it turned out, one of the panels was under the possession of Faust. When Masahiro Nabeshima awoke in the basement lab of nascita, he recognised the compartment in the wall used to check for Best Match combinations of the Full Bottles as being similar to the panel he saw in Faust's headquarters. Sento decided to break apart a section of the wall, only to discover that the other missing panel had been in Soichi Isurugi's possession all this while. As Soichi returned from work, Sento confronted him about the panel.
Soichi eventually revealed that he was the one who activated the Pandora Box, but he has no idea why, even in the present. It's possible that the Pandora Box influenced him into activating it on Earth after he discovered it on Mars.
Transference between parties
Seeing it as an opportunity to incite a war so as to push for Touto's use of the Kamen Rider system for military purposes, Gentoku Himuro/Night Rogue began an operation for Faust to infiltrate the Institute to steal the Pandora Box. Though the operation was slightly deviated due to Blood Stalk's intervention, Night Rogue eventually reclaimed the Pandora Box and kept it in a hidden location, unknown to even Blood Stalk himself.
The location turned out to be in a secret basement of one of Nanba Heavy Industries' laboratories. Blood Stalk managed to regain possession of the Pandora Box, much to Night Rogue's anger. Blood Stalk, having become Nanba's new working partner, kept the Pandora Box in a storage facility belonging to Nanba Heavy Industries. Build managed to overpower Blood Stalk and claim the Pandora Box using his newly attained OctopusLight form, bringing the Box back to nascita, though the Box would end up back in Nanba's possession yet again due to it, along with the Fullbottles, being taken by Soichi, who turned out to be the true identity of Blood Stalk.
It turned out that Soichi had made use of Sento's transformations into Build as well as Misora's power of purifying Fullbottles so as to fulfill his plan of obtaining 10 pairs of Best Matched Fullbottles so as to open up the Pandora Box. Jusaburo Nanba, CEO of Nanba Heavy Industries, planned to harness the energy source within the Pandora Box to create a weapon more powerful than nuclear arms. However, upon finding out that most of the Fullbottles stolen were nothing more than just fake replicas created by Sento, Soichi decided to confront Sento at the place where they first met each other. Transforming into their respective forms, Build eventually managed to overpower Stalk using his new RabbitTank Sparkling form, created using a component of essence from the Pandora Box. Soichi then decided to leave the Box with Sento once again, saying that he could take it back whenever he wanted to.
- The object's name is a reference to the similarly named Pandora's Box, a dangerous object from a story in Greek Mythology said to contain all the evils of the world. The Pandora of which the box is named after was the first woman created, who was told by the Gods to guard the box but never to open it. However, curiosity got the better of her and she opened it, resulting in entities that embodied pain, death, hate, sickness, sorrow, and so much more to be unleashed upon the world.
- The lack of the "apostrophe-S" in the name may either be a stylistic choice to make it stand out from the story's version or a mistake stemming from said grammatical construct not being present in Japanese.
- The evils released from the box are similar to the Smash created from the Box's unknown power.
- Some variants of the story note that "Hope" remains in the box after all the evils are released. This could be symbolised by Sento, as Build, being the hope of the country against the Smash, and how his power is fueled by the defeated "evils"/Smash through their conversion into Fullbottles.