Would the Icy Prison spell work differently against incorporeal foes?

Question

Would the Icy Prison spell work differently against incorporeal foes? I'm asking because I haven't been able to find anything about it, but this sentence under the Incorporeal monster rule makes me wonder if there's any specific interaction:

Incorporeal creatures cannot make trip or grapple attacks, nor can they be tripped or grappled. In fact, they cannot take any physical action that would move or manipulate an opponent or its equipment, nor are they subject to such actions.

Of course this is beside the 50% chance to affect incorporeals.

So, would the spell work but the creature could move out of the ice, could it only make incorporeal creatures entangled or would it not work at all?

Answer 1

RAW, there is no reason Incorporeals are affected differently. This means that:

1. They get their normal 50% chance to ignore the spell's effects, as per the rules for incorporeals.
2. Then they get their normal Reflex save.
3. If they fail their saving throw, they get encased, and could move out of that encasing if they hadn't been helpless as well (which Ice Prison directly and explicitly inflicts on targets failing their saving throw.).
4. If they succeed it, they get entangled instead. There's no rule against Incorporeals being entangled (I thought there was, but I couldn't find it.)

Of course, not all of that makes sense. As a DM, I'd happily rule they ignore the spell. (And warn my players about it, as in "Are you sure you want to cast Icy Prison on this Incorporeal Creature which obviously won't be affected by it?")