Challange Rating
Term
Challange Rating ( CR) is an aggregate score of several statistics in a monster's stat block. A creature's Challange Rating is the average of two measurements: offensive challenge and defensive challenge. Each of these two categories have various characteristics, measurements, and weights affecting their final calculation.
This calculation should be a challenge equal to 4 equivalent 
Player Characters equal of the same level, that should technically should not result in any Player Character's reaching the 
Dead status if both side are starting at full resources.
d100
Mod
ADV/DIS