Okay, I looked around and couldn't find it? I apologize if this has already seen the light, but I'm bringing it back into the light.
If a polymorph spell causes you to change size, apply the size modifiers appropriately, changing your armor class, attack bonus, Combat Maneuver Bonus, and Stealth skill modifiers. Your ability scores are not modified by this change unless noted by the spell.
Look at size changes.
Does Natural Armor count as an ability score? If not, why is it on this chart?
Does increasing size via a polymorph spell increase your natural armor to compensate for the loss of DEX and the penalty from increased size?
I know the spells do. But would this give you a little extra? The polymorph school doesn't say they don't, and it says apply the size modifiers appropriately, the natural armor bonus would be from increased size, and is not excluded like the ability scores.
You don't automatically get anything on the list for changing size except the derived bonuses inherent to being a different size. That is, you don't get a STR bonus or DEX penalty (note the spell gives you this separately) nor a NA bonus. You get the attack roll and AC penalty, the reach, the increased size, the skill penalties (to Hide), and the CMx bonuses that are inherent to being a different size.
Is that RAW or RAI? Where does it say that I don't get the stuff from changing size unless it says I do?
Shouldn't matter if I'm looking at the monster advancement table. That's the standard for anything that becomes sizes larger or smaller (with the exception of polymorph spells).
If you're not allowed to be affected by things intended for monsters, you wouldn't be allowed to take the stereotypical "monster feats" like improved natural armor, or Multi-Attack.
Shouldn't matter if I'm looking at the monster advancement table. That's the standard for anything that becomes sizes larger or smaller (with the exception of polymorph spells).
If you're not allowed to be affected by things intended for monsters, you wouldn't be allowed to take the stereotypical "monster feats" like improved natural armor, or Multi-Attack.
That's the problem. You're NOT supposed to be able to use Improved Natural Armor and Multiattack and stuff.
I believe there is a statement in a book, or by a Dev, or whatever, that says the only way you can take "monster feats" is by GM fiat.Using your example, you can't choose which chart you apply effects from.
Or else I would take levels in fighter, and use the spells per day of a sorceror, or some other scenario.
Note: that is only an example, and wouldn't work. I know.
You can't just pick and choose between charts you want to apply.
The size changes chart is a specific chart in the CRB. That's the one you HAVE to use.
"Monster Feats" are specifically stated as player available IF they qualify. If a Dev has stated they are not available then please post it, I do not believe there is.
Most of the following feats apply specifically to monsters, although some player characters might qualify for them (particularly Craft Construct).
Regarding Natural Armor:
Each polymorph spell allows you to assume the form of a creature of a specific type, granting you a number of bonuses to your ability scores and a bonus to your natural armor.
So, not the change itself, but the spell is what grants you a natural armor bonus.
If a polymorph spell causes you to change size, apply the size modifiers appropriately, changing your armor class, attack bonus, Combat Maneuver Bonus, and Stealth skill modifiers. Your ability scores are not modified by this change unless noted by the spell.
So, you use size modifiers to AC, attack, CMB, and Stealth. It does not state size modifiers to Strength, Dexterity, Constitution, or Natural Armor.
So, lets look at where the Size Modifiers are listed:
Attack/AC: CRB p179 Table 8-1
CMB: CRB p198
Stealth: CRB p106
If a polymorph spell causes you to change size, apply the size modifiers appropriately, changing your armor class, attack bonus, Combat Maneuver Bonus, and Stealth skill modifiers. Your Ability Scores are not modified by this change unless noted by the spell.
Isn't the bonus to Natural Armor given by increased size? Thus, wouldn't it qualify for the purpose of the "armor class" given as the modifiers to apply?
Also you said
CRB p212 wrote:
If a polymorph spell causes you to change size, apply the size modifiers appropriately, changing your armor class, attack bonus, Combat Maneuver Bonus, and Stealth skill modifiers. Your ability scores are not modified by this change unless noted by the spell.
So, you use size modifiers to AC, attack, CMB, and Stealth. It does not state size modifiers to Strength, Dexterity, Constitution, or Natural Armor.
My emphasis is on the part I went ahead and bolded, it specifically says that you do NOT gain the ability scores. It doesn't say anything about the Natural Armor Bonus.
You only change what a spell says is changed. There is no affecting size vs natural armor score. If they intended for the two to be connected they would say so. Your armor class is affected by size changes because you can get penalties and bonuses to your armor class based on size. That size bonus or penalty is in the monster stat block and has nothing to do with the natural armor penalty.
Note that it says they are "size modifiers". Then it goes on to list armor class, attack bonus, combat maneuver checks, and stealth skill modifiers which are affected directly by your size.
If you look at a monster it will have a natural armor bonus AND size bonus/penalty as two separate things.
Your size can also affect your dex and strength, and these specific changes are noted by the spell. You will never find a correlation that dropping down to size X or increasing to size y affects your natural armor bonus by ____ as a general rule because none exist. You may however find that using polymorph spell X affects your natural armor bonus by ___ amount, but that is due to the spell, not the size.
If you need more proof compare two spells that such as beast shape, and form of the dragon that increase your size by the same amount yet the increase in natural armor is different.
Also the game has "game terms". RAW and RAI natural armor is not an ability score.
Ability Score: Each creature has ability scores: Strength, Dexterity, Constitution, Intelligence, Wisdom, and Charisma. These scores represent a creature's most basic attributes. The higher the score, the more raw potential and talent your character possesses.
The monster advancement table and monster creation tables are guidelines for when a GM builds monsters. They are not rule for changing a monster's size.
Building the Monster
The following guidelines are provided to assist in monster creation and to help balance a creation for its CR.
D'oh!
If you look at a monster it will have a natural armor bonus AND size bonus/penalty as two separate things.
Here I was, thinking that the Natural Armor bonus was in and of itself a size bonus. I didn't put two and two together there.