Hello I have a question about Mirror's Reflection.
Is it possible to avoid an area effect if the character decide for example to choose that reflection affected ?
Thanks for your future answer.
No.
Anything that targets or would affect your reflection affects you and uses your statistics.
Scenario: Character has used Mirror's Reflection, so the character now has two locations that they could potentially be in. Fireball is cast such that only one of the locations is in the area of effect.
Even if the player is allowed to designate the affected version as the illusion, the illusion being affected would still cause the character to be affected. So they are still making a save against Fireball and taking the appropriate amount of fire damage.