Can I have multiple active instances of resist energy?

Question

Is it possible to have 2 or more castings of Resist Energy (or Protection from Energy or Draconic Reservoir), each covering a different energy type, active concurrently?

The CRB (5th, p209) says (emphasis mine):

Same Effect with Differing Results: The same spell can sometimes produce varying effects if applied to the same recipient more than once. Usually the last spell in the series trumps the others. None of the previous spells are actually removed or dispelled, but their effects become irrelevant while the final spell in the series lasts.

'Usually' implies cases where they do not trump the others - is there any official statement on when they should/should not?

Answer 1

This GM would say yes to multiple resist energy effects were energy types different

The Pathfinder Core Rulebook isn't allowed by the Open Gaming License to reprint the example from the Player's Handbook for Dungeons and Dragons 3.5 for the section of the rules that the question quotes, and Paizo deigned not to include its own example. This kind of absence leaves Pathfinder players sometimes at a loss as to the scope of the rules as originally presented in that game's antecedent. To fill that gap, presented below, for comparison and critique, is the Player's Handbook Same Effect with Differing Results paragraph:

The same spell can sometimes produce varying effects if applied to the same recipient more than once. For example, a series of polymorph spells might turn a creature into a mouse, a lion, and then a snail. In this case, the last spell in the series trumps the others. None of the previous spells are actually removed or dispelled, but their effects become irrelevant while the final spell in the series lasts. (172)

(Emphasis mine; the 3.5e SRD on this topic also omits this example.) I assume, based on this example, that the rule's supposed to quash shenanigans—like the player saying his PC should have the lion's ability to bite, claw, and roar while the PC's in snail form—, rather than to prohibit absolutely a creature from benefiting from a spell cast on it multiple times despite each iteration clearly having a differing effect and each iteration clearly not interfering, overlapping, or supplanting other iterations. Obviously and as always, each GM must determine the extent of this rule's application, but to this GM the spell resist energy seems like a fine candidate for an exception to the Pathfinder-added usually.

Answer 2

That section from the CRB is explaining how spells usually work. It's not providing prescriptive rules from the game, it's just explaining to you what usually happens, because usually multiple copies of the same buff spell don't really do anything since their same-typed bonuses don't stack, or because they give you an option for their duration and multiple sources of access to a single option isn't really helpful, or because they grant immunity to some source of danger, and additional immunities to that single thing are rarely helpful.

So, generally, you can have multiple active instances of any spell, the additional instances just don't do much.

That said, the specific spells in question do limit via their text their interactions with one another. You can certainly have Protection From Energy (fire) and Resist Energy (Acid) up at the same time, but if you instead ward against a single energy type, the reservoir provided by Protection from Energy is not protected by the Resist Energy effect.

Draconic Reservoir specifies that it does not stack with Protection from Energy, but technically that doesn't prevent you from using it alongside that spell. When two beneficial effects don't stack you have to take the largest bonus, so doing so gets weird since what the 'largest bonus' is supposed to be in this context is unclear. In my experience, people tend to have the pool with the most points left in it at the time apply to any given attack.

Stacking any of these spells with itself is in no way proscribed, and generally significantly increases the defensive effects:

Protection from Energy and Draconic Reservoir can each be self-combined either to provided separate pools for multiple energy types or to create what is effectively a larger single pool for one energy type.

Resist Energy Energy resistance from multiple sources stacked in 3.5, except that energy resistance not from spells couldn't stack with energy resistance from spells. Pathfinder kept this rule, almost verbatim

James Jacobs, creative director for Pathfinder, however, has said that "Energy Resistance does not stack". No explanation for this counter-textual ruling has thus far been provided, except that being a tiefling infernal bloodline sorcerer is supposed to "suck for [electrical resistance]", at least until level 20.