Difficulty Factor is one of the more obscure power factors in the collective and based on DM’s can have different qualities to its values. It originated from a campaign where a living dungeon called "The Trap" that would run the PC's against progressively harder monsters and by like DL C (which is 100), the Dungeon starts farming XP from the PC's. A similar example is the Shangri-La campaign where lower DL monsters were using higher DL spell and psi effects as well as having higher AC's and hp. DF begins at a value of 10 and for each DF higher than 10, the monsters use effects that are +1 higher SL. I have two separate DF ratings. One is for AC/hp and the other is for higher SL's. Higher DF also gives more XP.