...because I have gone over the table in the rulebook like 5 times and I can make neither heads nor tails of it. I think it is the most cryptic, vague, and generally arcane table I have seen yet in the Pathfinder Rules.
Maybe it's just because it's currently 1:30 AM here, but I am just failing hard right now.
Can anyone decipher this maddening riddle for me? Basically, I am trying to figure what changes between CR 2 and 3.
Thanks a bunch.
It depends on the monster type how many HD you have to add, and in addition CR is more of an art than a science. The advancement table in the book is what you should be looking at, as a general rule, to know how many HD are needed to go from one CR to another one.
Step 1:CR 2 to 3 results in 10 additional HP (table: Monster Advancement)
Step 2:10 additional HP result in 2 additional HitDice (10/4.5 or 10/5.5)
Step3 : No changes on attributes if the creature dont increase in its size (Hit Dice increased by 50% or more)
Step 4: New skill points by INT (minimum 1) per new hit dice. One new feat.
Step 5: Add the changes from the table Monster Advancement to AC, attack rolls, and damage rolls.
In most cases it is easier to add class levels to a creature or (if it is not able to take class levels) you use templates.
Adding the hitdice is easy, it's figuring out how many to add for a given CR that's the hard part.
Hitdice work like classes when it comes to actually adding them. They grant bonuses to BAB and saves like class levels, and also cause feats and ability increases to be gained like class levels. (A feat every other level, an ability increase every 4 levels). Adding hitdice will also probably change the DCs for special attacks, but usually not for spell-like abilities. Which race the creature is determines its hitdice, BAB progression, save progression, and class skills, and that information is found in the details of the Types.
There's the caveat that doubling a creature's racial hitdice may cause its size to increase as well, which will affect attack bonus, AC, space/reach, STR, DEX, etc, but that's not always the case.
If you're just wanting to add hitdice, it might be easier to add your hitdice then see what CR you hit. Usually adding racial hitdice seems to take the CR up slower than adding class levels. But, as someone said above, CR is more art than science, so it may take some eyeballing. I'm convinced everything in my campaign is over-CRed.