The Mystic Tower had a total of 8 floors that categorized tasks from least to most difficult.
Hidden Death Valley was a place for geniuses, but not all geniuses had the same starting point or classifications. For instance, there were even kids in Hidden Death Valley who hadn't reached 16 yet.
The lowest floor's tasks were doable even by 2nd class beings. These were usually patrol tasks or cleanup tasks in the portion of Death Emperor Star that'd already been claimed by the academy.
The difficulty of tasks jumped with every floor one climbed in the Mystic Tower. By the 5th floor, tasks began appearing that even the strongest 3rd class beings couldn't face.
Damien didn't stop at the 5th floor, though. These tasks were around the level an early 4th class being could handle, but that didn't apply to him. The tasks he wanted could only be on the 6th floor.