Stage Challenge is a feature that allows you to level up your Stage Panels by taking on a Challenge Battle.  Stage panels can be purchased and trained with medals earned from battle passes and missions.  The more you train and acquire new Stage Panels, the more Panel Points you'll receive. 

These Panel Points can be used to obtain a variety of rewards! You'll also unlock new Challenge Battle content, including new solo and 4-player Challenge Battle-exclusive modes.

*To unlock Stage panel training, you must purchase certain number of stage panels.