Associated Class Levels
Class levels that increase a monster’s existing strengths are known as associated class levels. Each associated class level a monster has increases its CR by 1.
很明显这些是描述。。
Barbarian, fighter, paladin, and ranger are associated classes for a creature that relies on its fighting ability.
Rogue and ranger are associated classes for a creature that relies on stealth to surprise its foes, or on skill use to give itself an advantage.
A spellcasting class is an associated class for a creature that already has the ability to cast spells as a character of the class in question, since the monster’s levels in the spellcasting class stack with its innate spellcasting ability.