So, as part of my upcoming campaign, I'm going to be reflavoring the devils quite a bit (the randomness of the Baatezu race has always bothered me, so they're getting a bit of a japanese cenobite reflavoring). Anyway, as part of this conversion, I was going to simply swap out their immunities to cold and give them cold immunity, rather than fire (while conversely giving demons fire immunity). I figured I would simply switch abilities like fireball into "ball of cold" and such. Can anyone think of any major mechanical repercussions for this? I know fire damage is a bit more common, but I don't think that's going to completely ruin my campaign. Thoughts?
As far as the mechanics of the game are concerned, no one energy type is just as good as another. You'll just have to factor in the idea that: In Pathfinder, fire is way more common. Aside from the plethora of spells based around fire in different shapes and forms, think about mundane fire. It's used daily in most medieval settings and its something that can spread like... well, wildfire. If you're going to have this spice, I'd suggest either having cold-based "fires" that burn blue or something equally cheesy, or alternatively, have some sections of freezing arctic waters. cold damage for swimming through them seems like it's surviveable, but when you realize that your still wet, it starts to seem a lot more like lava than you'd like.
Just a few suggestions to make the transition more balanced and immersive. Anyways, sounds like a cool idea. pun intended.
Those are good suggestions, thanks. And, now that you mean cheesy blue coldfire, it'd be easy enough to lump the 'turns fire blue' witch folklore in with devils and give them all the ability to make mundane fire 'burn' cold.