"Photon Metal" is a material used to build Core Deck Cases. Magoroku Shido requested Rouga Aragami to steal some Photon Metal from the Fuji Photon Metal Mine for unknown purposes. Rouga succeeded in stealing the Photon Metal using his Dark Core deck case despite the Buddy Police's intervention. That same night, Azi Dahaka revealed that he was the one who gave the order to steal the Photon Metal.
The stolen Photon Metal was presumably used to mass produce Dark Cores for Disaster's use.