Differentiating The Effects Of Size From Racial Ability Score Modifiers
Smaller creatures have low Str and Con, but high Dex, while larger creatures have crappy Dex and sometimes absurd levels of Str and Con. Normal D&D rules scale up (or down) Str, Dex, and Con with size. Now, they also adjust a large number of other factors alongside these that the three ability scores also usually impact in and of themselves (attack rolls, AC, weapon damage, Hide checks, combat maneuvers, etc.), which kind of means you get two different effective modifiers to the same thing from the same source for the same conceptual reason, but that's a whole other can of beans beyond the scope of what I'm working on here, so I digress.
Now, here's an issue. How much of Str, Dex, and Con come from a larger or smaller creature being inherently better in that regard (like an Orc, Elf, or Dwarf), and how much come from the creature just having more mass to throw around because of its raw size? How much of a creature's strength should be from race and how much should be from size?
Since this question involves normalizing for size, it also serves as an effective start to standardizing the influence of size-changing effects. There are numerous ways to change in that, unlike Polymorphing, provide modifiers to the creature's ability scores instead of setting them to a fixed value. Unfortunately, the actual numerical effects of these different methods rarely agree with one another. The Enlarge and Reduce Person spells give one set of adjustments and Righteous Might gives another. Size change from monster HD advancement and template application is variable, the modifiers depending on the starting and ending sizes. The Wu Jen spell Giant Size changes to a specific size, and gives a fixed set of modifiers depending only on the ending size, not the starting size, even providing the massive Strength boosts associated with size growth despite the fact that large enough casters may even be shrunk by the spell.Modifiers By Size
After looking through the various spells that modify size in Core, the monster growth table, and peeking at a small sample of monsters at various sizes, and adjusting to curb some of the worse excesses of Str growth with size, I've come up with a table of Str, Dex, and Con adjustments by size. This is my quick and dirty evaluation of the amount of a creature's racial ability modifiers I am approximating to come from raw size alone, using a Medium creature as the baseline. The rest of the racial ability score adjustments are exactly that, coming from the race's natural inclinations to be better or worse than the norm. Note that the numbers still definitely need tweaking.
|Size Category||Str||Dex||Con||Natural Armor|
Alternatively, stat changes when going from one size category to the next. This may be more convenient when considering the direct effects of size-changing effects.
|Old Size Category||New Size Category||Str||Dex||Con||Natural Armor|
For example, a Minotaur is a Large creature with +8 Str, +0 Dex, and +4 Con racial adjustments normally. In order to break that down into which part is racial and which part is raw size, we have to remove the size components. According to the table above, we can expect its size to be giving it +4 Str, -2 Dex, and +2 Con. Taking that away from the total modifiers it has means that the Minotaur's actual racial modifiers are +4 Str, +2 Dex, and +2 Con, the rest coming from its size.
Similarly, we can look at a Gnome. At size Small, it normally gets -2 Str and +2 Con. This breaks down into -2 Dex and +2 Con racial adjustments, plus the -2 Str and +2 Dex from its size.
Note that none of what's been described so far actually changes anything. The final ability scores a creature has are exactly the same whether it's a single racial modifier or broken down into a combination of racial and size modifiers.Size-Changing Effects
The only real mechanical changes this is good for is for standardizing size-changing effects. Currently, they're all over the place. With this, we can rewrite them all to remove any specific values. Enlarge Person no longer gives a fixed +2 Str and -2 Dex. Instead, like all size-changing effects, it just changes your size. The size change itself changes your ability scores, since you'll be using the modifiers for your new size in place of your old. Ditto for Reduce Person, Righteous Might, and Giant Size.
You may notice that this results in a pretty serious buff to Enlarge Person. This is true with the numbers posted above. As I said, it's a quick and dirty approximation. It definitely needs tweaking and adjustment.Advancing Monsters By Size
The table I posted above, you may notice, is roughly half what the Table: Changes to Statistics by Size in the Monster Manual gives. I kinda figured that roughly half of what monsters were getting from advancing size categories was just bulking up, and half was from advancing to be noticeably stronger and tougher independent of size. Of course, the table still gives some absurdly large changes to Str, so it's you're choice whether you want to replace those adjustments with the table above or just assume that the other half of things is actual additions to the racial ability bonuses.