Sadras
Legend
Apologies, I might have missed the answer to this question, but given that definition of a creature, how does one rule on magic missile being cast to hit a creature which is secretly an illusion?
D&D 5E Magic Missile vs. Mirror Image
Apologies, I might have missed the answer to this question, but given that definition of a creature, how does one rule on magic missile being cast to hit a creature which is secretly an illusion?
Maxperson
Morkus from Orkus
Or a golem, which would also be an object.
Maxperson
Morkus from Orkus
This is nonsensical. The 2e and 3e versions, like the 1e and 5e versions also could not possibly miss the target creature, and could only target creatures. They also specified that the spell did not affect objects that it struck. So, a spell that cannot miss the target creature explained that it could not effect inanimate objects. Why is that do you think? Is it because it wasn't possible to hit those objects with the spell, or because it would be nonsense to think that the spell would just fail to happen completely if you say aimed it at a wall? I'd bet good money that Gygax got tired of people asking him if you could aim a 1e MM at a sword and having to respond that, yes it just makes sense that you can aim it at anything, but it can only affect creatures, so he threw that bit about objects into 2e. I see no reason why 5e would be any different.
toucanbuzz
No rule is inviolate
Multi-layered answer and I didn't scour the first 40 pages of posts. First, the original post regarding whether magic missiles affect mirror images has been adjudicated by Sage Advice, which Wizards holds as "official" rules clarifications.
Sage Advice says Magic Missile is unaffected by Mirror Image. It will hit the creature you're aiming for, even if you are seeing double. In short, by their nature, Mirror Images deflect things that require an attack roll, nothing else.
But, other illusions, yes Magic Missiles can be aimed at an illusion, if it's a creature illusion. Let's start with Minor Illusion, the cantrip, which can only create an object. The more powerful version Major Image can generate a creature, and this distinction is important because each illusion creates something that can be targeted by some spells and not others.
Illusion spells "deceive the mind." Jeremy Crawford once said in a podcast (non-canon) regarding "invalid targeting" that he envisioned the spell creating a link between the caster and target. Generically, illusions aside, if you targeted a non-creature with Magic Missile (e.g. a gargoyle statue), there would be no link, the spell couldn't work, and you'd lose the spell slot. This is consistent with the subsequent (optional) rule in Xanathar's Guide for Invalid Targets (adding that if the spell had a save, it'd appear the target saved so the caster doesn't get a heads up about the true nature of the target).
Notably, illusions are described as spells that "deceive the mind." The caster is fooled into believing there is a creature to target, and this deceit will be dispelled when there is physical interaction with the illusion. Once the missiles interact the ruse is up.
So, in summary. You can aim Magic Missile at anything you want. If it's a creature illusion revealed on physical interaction, your missiles will at least make contact and tell you it's not real. Mirror Image is distinguished because it only deflects things that require an attack roll, and that conversation has been exhausted enough I won't repeat it other than the conclusion that you can't aim Magic Missiles at Mirror Image duplicates.
As to the Golem question, a golem is a construct and counts as a creature. The Xanathar Guide rule on Invalid Targets would, however, make your spell invalid if you believed a simple statue were a golem. Depending on the spell, the slot would either be wasted, or the target would appear to save.
Magic missile obviously has some kind of homing mechanism that directs it to a living creature. So just sending it toward the general area of a creature will do the trick. I agree with [MENTION=23751]Maxperson[/MENTION] that there are distinct duplicates that can confuse an attacker relying on sight. This is not a case of a shimmery armor, but actual deception (even though the duplicates occupy the same grid space but as that is a five foot square there’s plenty of room 
)
)Short answer, RAI - You waste your action but you don't lose the spell slot. The rules on this are vague though, so check with your DM.
Long answer: https://www.reddit.com/r/dndnext/comments/5ozpwj/jeremy_crawford_on_targeting_spells/
I've always viewed Magic Missile as an attack that auto-hits with no need for a roll. Not precisely the 5e wording, but that is my interpretation of the intent. Mirror Image is a spell that, unlike other defenses, does not increase the AC of the recipient (which would be a slam dunk for MM to bypass); but rather introduces the chance that the attack will target an image. MM still requires a target, even sans a roll. I don't have a problem with MM hitting images as a clever caster will target as many 'duplicates' as possible with MM and likely eliminate all of them with a possibility of striking to 'real' creature. The spell still proved useful, as it completely cancelled out a second level defensive spell. I don't by the 'can only target a creature' logic, as that would prevent the spell from being used against an illusory creature designed to fool the caster, thereby making it an automatic illusion detector. The duplicates are definitely illusory creatures.
I realize this goes against the Sage, but the Sage's ruling relies on a rules-lawyery definition of 'Attack' that more than likely did not take MM into account when it is written. That said, I can see the other side of the argument and I am not strongly opposed to it.
I realize this goes against the Sage, but the Sage's ruling relies on a rules-lawyery definition of 'Attack' that more than likely did not take MM into account when it is written. That said, I can see the other side of the argument and I am not strongly opposed to it.
I try to look at it from a player point of view - keeping in mind that players can be on either end of this particular showdown.
As a player, if I cast magic missile targeting an NPC wizard under mirror image, I'd be happy if I could blast away all of the images, but I wouldn't feel hard done by if my missiles all bypassed the illusion and went straight to the enemy (full damage but the illusions remain intact). That's still good value for my spell slot.
On the other hand, if I were under mirror image and an NPC wizard erased it with a single casting of magic missile, I'd feel a bit cheated. Not only have the images failed to save me much damage, there's no excitement in it. Half the fun of a spell like mirror image is rolling to see if you can divert the enemy. Do you get to thumb your nose at them? Or do you get pounded flat? Having the missiles bypass the illusion is more satisfying all around - the enemy wizard has put a shot through my defenses, but I'm still protected from her fighter allies, and now I know who I have to take down.
So, all in all, I think this one is more fun when played by the book.
As a player, if I cast magic missile targeting an NPC wizard under mirror image, I'd be happy if I could blast away all of the images, but I wouldn't feel hard done by if my missiles all bypassed the illusion and went straight to the enemy (full damage but the illusions remain intact). That's still good value for my spell slot.
On the other hand, if I were under mirror image and an NPC wizard erased it with a single casting of magic missile, I'd feel a bit cheated. Not only have the images failed to save me much damage, there's no excitement in it. Half the fun of a spell like mirror image is rolling to see if you can divert the enemy. Do you get to thumb your nose at them? Or do you get pounded flat? Having the missiles bypass the illusion is more satisfying all around - the enemy wizard has put a shot through my defenses, but I'm still protected from her fighter allies, and now I know who I have to take down.
So, all in all, I think this one is more fun when played by the book.
FrogReaver
As long as i get to be the frog
Apparently there is a third option present which is how I have always played magic missile and mirror image.
The magic missile only targets the caster as normal and cannot directly target the images. However since mirror image allows the caster to roll a d20 to determine if one of the images takes the attack instead of him then I do that to magic missile as well and that is the only time it is allowed to hit the mirror image.
The magic missile only targets the caster as normal and cannot directly target the images. However since mirror image allows the caster to roll a d20 to determine if one of the images takes the attack instead of him then I do that to magic missile as well and that is the only time it is allowed to hit the mirror image.
