D&D 5E Magic Missile vs. Mirror Image

[Maxperson]

If you think so then you should houserule mirror image to say that it can redirect any effect that targets the caster, not just attacks.

Well, it just makes sense. Anything a caster can see and target, a fighter can also see and target. Mirror image only makes sense if it affects both types of attacks.

 

[Cognomen's Cassowary]

What's good for the caster is good for the martial. If the fighter can't tell who the caster is when he "targets" with an attack, a spell caster should similarly be unable to tell who the caster is when choosing a target for his magic missile or other spell. Mirror Image should apply equally to both martial and casters.

Okay, and what about magic missile? Should it apply equally to both martials and casters? Under your house rule to allow mirror image to redirect magic missile, do you also allow AC to deflect it?

 

[Caliban]

Yeah, this is how I play it. Detection magic shouldn't be cheapened or made obsolete.

BTW, thanks - this whole discussion has been really good. It's really clarified my thinking on these spells.

Yeah, but that will still tell you if the chest is a mimic or not. It just changes the point at which the information is gained.

Did it take damage from Eldritch blast? If didn't, then it's an object. If it does take damage - MIMIC! (Or animated object, etc.)

Still, requiring them to actually cast the spell is an improvement.

 

[Sorcerers Apprentice]

Well, it just makes sense. Anything a caster can see and target, a fighter can also see and target. Mirror image only makes sense if it affects both types of attacks.

It's all magic though, it doesn't necessarily have to make sense

 

[Maxperson]

Okay, and what about magic missile? Should it apply equally to both martials and casters? Under your house rule to allow mirror image to redirect magic missile, do you also allow AC to deflect it?

It does apply to both martial and casters equally. It hits exactly what it aims for 100% of the time. Mirror Image doesn't deflect anything, so neither does AC. If an image is aimed for by the caster, it is hit 100% of the time, just like someone in armor.

 

[Maxperson]

It's all magic though, it doesn't necessarily have to make sense

Yes and no. Magic can break reality, because magic. However, it still has to make some semblance of sense in the way that it does it. Nobody is going to sit down and design a spell that creates images that fool the mind, but only if you're trying to hit the caster. The image is going to fool anyone looking at it that doesn't have a way around it like true seeing. Even for magic, it doesn't make sense

 

[Cognomen's Cassowary]

It does apply to both martial and casters equally. It hits exactly what it aims for 100% of the time. Mirror Image doesn't deflect anything, so neither does AC. If an image is aimed for by the caster, it is hit 100% of the time, just like someone in armor.

But that doesn't, to use your terminology, make sense. AC is a composite of many factors, including physical armor, magical armor, evasiveness, and cover. In order to always impact, magic missile must be able to avoid all of that--arc around cover, track a creature trying to dodge, and strike it where it is vulnerable. What you are suggesting is that, in fiction, the caster aims the spell to do all of that . . . and never misses. (Unless the caster is fooled into aiming at an illusion.)

I would consider it a more parsimonious explanation that it is part of the magic of the missile that allows it to avoid all of those various things. I see no reason why the magic should be less capable of detecting and overcoming a mirror image than it is, for example, mage armor.

 

[Maxperson]

But that doesn't, to use your terminology, make sense. AC is a composite of many factors, including physical armor, magical armor, evasiveness, and cover. In order to always impact, magic missile must be able to avoid all of that--arc around cover, track a creature trying to dodge, and strike it where it is vulnerable. What you are suggesting is that, in fiction, the caster aims the spell to do all of that . . . and never misses. (Unless the caster is fooled into aiming at an illusion.)

Correct. It never misses what the caster aims at. If the caster aims at an image, it will unerringly hit that image.

I would consider it a more parsimonious explanation that it is part of the magic of the missile that allows it to avoid all of those various things. I see no reason why the magic should be less capable of detecting and overcoming a mirror image than it is, for example, mage armor.

It doesn't detect mage armor. It just hits despite it. Being a force attack, it can impact armor and still do damage. It has no need to zip around to some sort of opening and hit there like you suggest. It will go around a corner or cover, but that's it. It also has no ability to tell the difference between one person and another. That's what the caster is for. The caster has seen his target and aims at it. The spell then avoids all but that target. It's not an intelligent thing.

 

[transtemporal]

An 'attack', however, is a lot more vague.

Right, so Mirror Image is basically dispelled by any damaging area of effect spell since those attacks automatically cause damage. But if that's the case, why bother with the phrase "A duplicate can be destroyed only by an attack that hits it"? Isn't that a bit redundant?

 

[Maxperson]

Right, so Mirror Image is basically dispelled by any damaging area of effect spell since those attacks automatically cause damage. But if that's the case, why bother with the phrase "A duplicate can be destroyed only by an attack that hits it"? Isn't that a bit redundant?

It's not redundant because there are attacks that can miss, and those would not destroy a duplicate.