Particularly powerful Shadowkind species have a Level Adjustment, which reflects how much more powerful these species are compared to "baseline" species (such as elves, dwarves, and humans). When you add this Level Adjustment to a character's total class levels (or character level), the result is a character's Challenge Rating (CR). The formula for determining a character's Challenge Rating (CR) is as follows: CR = Character Level + Level Adjustment
CR is used to determine a character's relative power compared to other characters.
A character's CR is never used to determine how or when a character gains new skills and feats, nor does it have any effect on talents, spells, and abilities that use character levels. However, a character's CR is used to determine how many experience points the character needs to advance in level (see Experience, below).