Multiple Spell Immunity and other spells

[__INT]

I am running Fists of the Ruby and my player wants to cast multiple spell immunity to counter enemies' spells such as Power Word: Stun, Maze, Roaring Applause, and Hideous Laughter.

But I refer to general rules in "Duplicate Effects" to stop him apply multiple Spell Immunity. Do I judge correctly?

CRB pg. 443 wrote:

Duplicate Effects

When you’re affected by the same thing multiple times, only one instance applies, using the higher level of the effects, or the newer effect if the two are the same level. For example, if you were using mage armor and then cast it again, you’d still benefit from only one casting of that spell. Casting a spell again on the same target might get you a better duration or effect if it were cast at a higher level the second time, but otherwise doing so gives you no advantage.

Similarly, can players cast multiple Resist Energy to get resistance for all of fire, cold, and sonic?

[Ascalaphus]

It depends on your interpretation of "the same thing". The example given, double Mage Armor castings, clearly wouldn't achieve much; Item bonuses don't stack.

But is "resist energy (fire)" really the same thing as "resist energy (acid)"? I think that's not so clear-cut.

Ironically, the very next item on that page in the book is about dealing with ambiguous rules. It advises you to ask "is it too good to be true?"

Looking at it from a different angle: spell immunity attempts a counteract check against the named spell. So for it to be any good, it needs to be sufficient level. A level 4 spell immunity spell couldn't stop a maze even if you got a critical success on the counteract check. A level 7 spell immunity would only stop the maze on a success, a level 9 maze would also stop it on a failure. So having real security against a single spell is pretty expensive.

Your player wants to to use a LOT of high level spell slots to protect themselves. That doesn't sound too good to be true to me.