The Chamber of Challenges is a dungeon with five different difficulties (INT, ADV, PRO, ELT, and LGD) that can be cleared to obtain red star quartz.

Red star quartz is an item that can be exchanged for enhancement units called "Doors" which can further increase the maximum limit of a unit's parameters.

For example, using a mini soul door on a unit whose SPR can increase by 65 will increase the SPR limit by 1 to 66.
Using a soul door on a unit whose SPR can increase by 65 will increase the SPR limit by 5 to 70.

Multiple doors can be fused to increase each parameter limit to up to 1.5 times the original value.

The dungeon can be cleared weekly with the challenge changing each week.