I would recommend waiting until you have at least finished the story line once, or filled out your Parameters skill tree along with your Equipment Slot Gain skill in the Exploration tree. This will allow you to maximize your speed, attack, defense, and flame-flame gauge with skills and items.
There are 4 challenges in the Sabo DLC:Mirror World
If I need to make any changes please let me know. The cut off times and kill count cut off need to be verified.