OK, it seems like Mirror Image is one of the worst culprits of spells (especially popular, low level core spells) for causing rules confusion. I thought it might be nice to have an FAQ/Q&A thread for Mirror Image.
Below I have spoilered the “official” FAQ entries regarding our friend, Mirror Image. I have also spoilered the SRD entry for the spell itself.
Now, I’m going to add to this list as I go, but here’s some of the questions I’ve often seen asked about Mirror Image (I will add more as people come up with questions and answers):
Q1 Can you shut your eyes (accepting a 50% miss chance) and simply ignore Mirror Image?
A1 Definitely yes. It's right there in the spell description: An attacker must be able to see the images to be fooled. If you are invisible or an attacker shuts his or her eyes, the spell has no effect. (Being unable to see carries the same penalties as being blinded.)
Q2 How does Magic Missile interact with Mirror Image? Do the missiles automatically target the real creature, or does every missile have a chance of striking an image?
A2 As per the FAQ: Any spell you can aim at a creature you can aim at an image. When you use a spell that allows you to select multiple creatures as targets, such as magic missile, you can choose multiple images as targets.
Q3 Do spells which target a creature, but not have a physical effect (Charm Person, for example) have a chance to target an image instead of the real creature?
A3 Yes, as per the FAQ: Any spell you can aim at a creature you can aim at an image. Whether this destroys the image or not isn't quite as clear. I believe the answer would be yes, as a Charm Person spell is considered an "attack" (as per the Invisibility spell, any offensive spell is considered an attack). As per the spell: Any successful attack against an image destroys it.
Q4 Do allies have a chance to “hit” an image with a beneficial touch spell, such as Cure Light Wounds? If they do, does this destroy the image?
A4 It would seem obvious that if an ally seeks to touch you with a beneficial spell or other effect, he would have to try and pick you from the images as normal. What isn't so clear, is if a touch with a beneficial spell would destroy an image. the spell states: Any successful attack against an image destroys it. The real question is whether this counts as an attack or not.
Q5 Does a fireball or other AoE spell destroy all images?
A5 No. As per the spell: Figments seem to react normally to area spells (such as looking like they’re burned or dead after being hit by a fireball).
Q6 How would Mirror Image stack with spells that grant concealment and a miss chance such as Blur? Would it be a case of 20% chance to miss whenever you make an attack roll against an image or only if you "pick" the real caster?
A6 The FAQ addresses this pretty directly: The images also look just like the caster, and they share purely visual effects such as the blur or displacement spell. If the mirror image user is also using either of these effects, an attack aimed at an image has the same miss chance an attack aimed at the caster has.
Q7 Do multiple casting of Mirror Image stack?
A7 No, Mirror Image would follow the normal spell stacking rules, and overlap rather than stack. A second casting would extend the duration of the spell, and if the number of images rolled for the new casting was greater than the existing number, that would become the new number of images.
