Icy prison vs cold immune creature?

[Yqatuba]

If you cast icy prison on a cold immune creature does it just have no effect at all? Or are they still encased in ice but don't take any cold damage? I would guess the second as even if they can't be hurt by cold that doesn't mean they can just ignore the fact that ice is forming around them.

[Fox Soul]

This is from my quick search:
"A creature with immunities takes no damage from listed sources. Immunities can also apply to afflictions, conditions, spells (based on school, level, or save type), and other effects. A creature that is immune does not suffer from these effects, or any secondary effects that are triggered due to an immune effect."

[Melkiador]

Sometimes the rules and magic of the game don’t make good real world sense. I usually think it’s faster just to go with the game logic. But ultimately, it’s up to the GM how much he wants to stick to the rules or how much he wants to simulate reality.

[Kayerloth]

Or think of them like rapidly flowing water ... the ice just never really forms solid/thick enough to effect them because of their immunity if you want to shoot for a rationale (other than 'it's magic') of some sort.

[Yqatuba]

Bonus question: if you cast icy prison on a monster that is so hot it does fire damage to anyone hitting/grappling does the ice itself take fire damage every round? I would say yes and it takes full damage instead of half.

[Temperans]

Well the ice does have 0 hardness & 3 hp per inch of thickness, so most damage could destroy really easily.

Wether the aura does half or full damage depends on how it works and wether fire always deals full damage to ice; which I have no idea for either.

[Nathan Monson]

Yqatuba wrote:

Bonus question: if you cast icy prison on a monster that is so hot it does fire damage to anyone hitting/grappling does the ice itself take fire damage every round? I would say yes and it takes full damage instead of half.

RAW, no, because the Ice is not hitting the creature with a natural attack/Unarmed strike or grappling it.

Technically, most auras specifiy Creatures and so would not damage the ice either.
That being said, having the ice take faire damage each round in those cases is a perfectly reasnoble call for a GM to make, and would probobly be RAI.