When adding class levels to a creature with 1 or less HD, you advance the creature like a character. Otherwise, use the following guidelines.
If you are advancing a monster by adding player character class levels, decide if the class levels directly improve the monster's existing capabilities.
When adding class levels to a creature, you should give it typical ability scores appropriate for that class. Most creatures are built using the standard array of ability scores: 11, 11, 11, 10, 10, 10, adjusted by racial modifiers. If you give a creature a PC class use the elite array of ability scores before racial adjustments: 15, 14, 13, 12, 10, 8. Creatures with NPC classes use the nonelite array of 13, 12, 11, 10, 9, 8. T
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.
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.
If you add a class level that doesn't directly play to a creature's strength the class level is considered nonassociated, and things get a little more complicated. Adding a nonassociated class level to a monster increases its CR by 1/2 per level until one of its nonassociated class levels equals its original Hit Dice. At that point, each additional level of the same class or a similar one is considered associated and increases the monster's CR by 1.
Levels in NPC classes are always treated as nonassociated.
When you improve a monster by adding Hit Dice, use Table: Improved Monster CR Increase to determine the effect on the creature's CR. Keep in mind that many monsters that advance by adding Hit Dice also increase in size. Do not stack this CR increase with any increase from class levels. In general, once you've doubled a creature's CR, you should closely watch any additional increases in its abilities. Adding Hit Dice to a creature improves several of its abilities, and radical increases might not follow this progression indefinitely. Compare the monster's improved attack bonus, saving throw bonuses, and any DCs of its special abilities from the HD increase to typical characters of the appropriate level and adjust the CR accordingly.
Table: Improved Monster CR Increase |
|
Creature's Original Type |
CR Increase |
Aberration, construct, elemental, fey, giant, humanoid, ooze, plant, undead, vermin |
+1 per 4 HD added |
Animal, magical beast, monstrous humanoid |
+1 per 3 HD added |
Dragon, outsider, nonassociated class levels |
+1 per 2 HD or 2 levels added |
Directly associated class levels |
+1 per level added |
Other Modifiers: |
|
Size increased to Large or larger |
+1 to CR |
Monster's ability scores based on elite array* |
+1 to CR |
Monster possesses special attacks or qualities that significantly improve combat effectiveness |
+2 to CR |
Monster possesses special attacks or qualities that improve combat effectiveness in a minor way |
+1 to CR |
Template added |
+ template CR modifier |
* Do not apply this increase if you advance a monster by class levels. (Monsters advanced by class levels are assumed to use the elite array.) |
|
Generally, increasing a monster's size increases its combat effectiveness. Large creatures gain increased Strength, reach, and other benefits. Apply this modifier if you increase a creature beyond Medium and in conjunction with any other increases.
Be careful, though. Monsters that benefit from a smaller size may actually lose effectiveness because of a size increase. Monsters that don't benefit from size increases don't advance in that manner for this reason.
You can add any sort of spell-like, supernatural, or extraordinary ability to a creature. As with a class level, you should determine how much, or how little, this ability adds to the creature's existing repertoire. A suite of abilities that work together should be treated as a single modifier for this purpose. If the ability (or combination of abilities) significantly increases the monster's combat effectiveness, increase its CR by 2. Minor abilities increase the creature's CR by 1, and truly trivial abilities may not increase CR at all. If the special abilities a monster gains are not tied to a class or Hit Die increase, this CR increase stacks.
A significant special attack is one that stands a good chance of incapacitating or crippling a character in one round. A significant special quality is one that seriously diminishes the monster's vulnerability to common attacks. Do not add this factor twice if a monster has both special attacks and special qualities.
Make sure to 'scale' your evaluation of these abilities by the monster's current CR.