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The Ark is a downed satellite that MetsubouJinrai.NET worships and the central antagonist of Kamen Rider Zero-One.
The Ark was created in 2012 by Hiden Intelligence in collaboration with a multitude of other companies at Daybreak Town. However, on the day it was supposed to be launched, MetsubouJinrai.NET struck and hacked thousands of HumaGears to turn rogue and go on a rampage. To stop the rampaging HumaGears, Hiden factory chief Satoshi Sakurai self-destructed the factory, resulting in the Ark being damaged and submerged underwater.
In the present day, Horobi and Jin of MetsubouJinrai.NET, hearing the Ark's judgment that humanity was a threat to the planet, began seeking to reawaken the satellite and use it to commence a HumaGear uprising against humanity. To accomplish this, Horobi had Jin use Progrise Keys and ZetsumeRisers to hack HumaGears close to reaching Singularity to turn them into Magia and collect their evolved data into the Keys. Once all the Keys had sufficient data, Horobi and Jin handed them all to Kamen Rider Ikazuchi, who used them to fully reawaken the Ark. The Ark then sent the data for the Assault Wolf Key to MetsubouJinrai.NET's base to be manufactured and began producing a massive army of Trilobite Magia for the crusade against humanity.
Despite Jin's army being destroyed by Kamen Rider Zero-One Assault Hopper, the Ark remained active and continued to hack HumaGears all on its own once they reached Singularity, turning them into Magia without the use of manual hacking through a ZetsumeRiser. However they can be restored to their original HumaGear state once their Magia form's are destroyed.