Obtained: Speak to the Mirage located just past the boss room in Film Set B, 1F of the Daitou TV Idolasphere.
After accepting the request, head further into the Idolosphere and defeat an Inferno, Blackscale Rider and Ironcad Knight to receive an Inferno Force, Blackscale Force and Knight Force. Once you’ve collected all the items, hand them over to the Mirage.
Reward: Treasure Key