Although Rhode wasn't able to bid for the Endless Forcefield successfully, it was something extra after all. Instead, the Maze Key was the crucial item and just obtaining it was good enough for Rhode.
And now, the pre-mission for the Castel Plateau Ruins mission awaited him: exploration of the underground maze.
According to the in-game players's excavation, this underground maze was situated in the Central Garden of Eagle City. The secret entrance would link to the underground maze through a tunnel and of course, this secret tunnel came with a long history… However, Rhode had no interest in how long its history was, nor how hair-raising it was. All he cared about was that this tunnel would lead him to obtain some equipment that would assist him in completing the main mission easily.