The Parallel Engine is a machine originally theorized by the Renaissance genius Leon Giordana for the creation of a massive amount of energy. Though merely part of his notes of future technology of the time, it would eventually be discovered by the Search Guard Successor Foundation, an organization who would utilize the notes as the basis of the development of technology for their purpose of finding and collecting dangerous Precious artifacts. The Parallel Engines were created by the SGS and used for the building of various vehicles for Precious acquisition. The engines would also be tied to a special suit developed to utilize their energy for human usage to allow for further search and management of Precious and those who would use them for evil purposes, making these users the "Boukenger