DerangedSquid's page

Yeah, re-reading Frostbite again, it is less clear than I'd originally thought that it is a buff rather than an attack. The only thing that really hints that it might be is the fact that it is a transmutation, and the targets line kind of implies the opposite. At the time I'd misread it and thought you could cast it on other friendly targets, and that it was clear that the target was the creature gaining the touch attack rather than the creature being attacked. Upon re-reading it, I'd actually read it the other way, meaning it would be an offensive spell and would qualify.

Given that, I don't think there is clear RAW on how these things interact. I could see several ways that would make sense. Personally, given that the secondary effects seem tied to targets rather than damage, I'd probably go with a once per target per casting sort of ruling, but I don't think that that is necessarily any more correct than just the first target, or on every touch attack.

When the spells to be commixed are cast, one is designated as the primary spell (typically the higher-level spell), while the other is the secondary spell. The primary spell must be an offensive spell that targets an area or one or more creatures. The secondary spell can be any spell with an appropriate descriptor.

I would read that as disqualifying Frostbite from being the primary spell, as frostbite isn't really an offensive spell, but rather a buff spell that grants a touch attack (as you cast it on yourself or a friendly target rather than on an enemy). It could still be used as the secondary spell, but in that case its normal effects would not manifest so the question would be moot.