So, my friends recently corrupted me with the anime Attack on Titan. For those of you who are unfamiliar with it, the plot details humanity's fight for survival against a race of creatures called Titans.
The titans look human, more or less, except for their gigantic size (most ranging approximately from 9 to 45 feet tall). They exhibit mindless behavior, their only real "need" being to seek out and eat human beings. They ignore all other life forms, and can seemingly continue to exist without eating humans for decades at a time (if not indefinitely).
Watching this gave me a direction to go in for the early-mid levels of my next Pathfinder game. Take creatures of the giant subtype, and make them zombies of varying flavors. One thing that caught my eye was the brain-eating zombie variant presented in Classic Horrors Revisited, which gives the zombie a bite attack with the grab special ability, with no increase to the zombie's CR.
I'm not really all that familiar with creating or customizing monsters outside of the presented rules, so I'm wondering if taking Large or bigger brain-eating zombies and giving them the Swallow Whole ability (limited to creatures at least two size categories smaller than they are) would increase the CR or not. What do my fellow GMs think about this? Any help on the subject would be greatly appreciated. :)
I would not alter CR at all for that, especially on Large zombies that can't swallow Medium creatures.
That's kind of how I was leaning, but again, I don't do much with creature customization so I wasn't sure if it would skew the balance in any way.
Certain abilities, even if they add power to the creature, do not alter CR.
For instance, at CR 10 or above (in PF standard magic), DR X/magic almost doesn't matter. DR 2000/magic is more powerful than DR 5/magic, but to the PCs, it might as well be the same.
Now, if you make them huge zombies and give them a really effective damaging stomach, they might be worth a slight bump in CR, but I'd really not give them much at all.