Bosh

This spell is particularly strong for Artificers, if they pick the MindSharpener Infusion.

MindSharpener turns any non-magical clothing or armor into a 4 use Concentration auto-saves (recovering 1d4 uses at dawn). With that combo, you can avoid most attacks, and auto-save in case you would loose concentration.

Blur as written is not a concentration spell though. Its just a flst 1 minute buff

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An enemy using green flame blade certainly doesn't mind your mirror image spell. There's a non-zero chance your duplicates are easier to hit than you are, so rolling against your duplicate gives a GFB fighter the opportunity to still splash damage on you. 

I think they're situationally relevant. A blur could protect from Sneak Attack-style damage and other such riders for slightly longer; even if the attacks hit, simply forcing them to be made with disadvantage has its purpose. 

 Correct me if I'm wrong, but I believe GFB would not work. GFB requires that you target a creature, meaning you have to target the caster, not a duplicate. And because a duplicate is not a creature, if you miss the caster adn hit a dupe, GFB would not leap over to the caster.

 “Creature” is a very broad term.

In this context, I would rule that the attacker perceives the illusion as a creature, and so they would still be able to target and hit it, hitting you with splash damage.

 

You're obviously free to rule that way at your table, but that's not how GFB or Mirror Image work RAW.

Illusions are not creatures unless explicitly stated as such. They aren't in this case. And there are good reasons for that. Like mentioned above they aren't affected by AOE. If they were creatures though, they would be. But what would their save bonus be? How much hp do they have? They have no stats. They could be targeted by other spells as well if they were creatures. Etc. Treating them as creatures raises a bunch of questions with no answers because they quite clearly are not meant to be treated as creatures.

Furthermore, the whole point of Mirror Image is the attacker doesn't know which one is real. So you can't choose to target a copy any more than you can choose to target the real creature (which again, would become untrue if the copies were creatures). You make an attack and it hits one of them randomly, and the GFB secondary damage is lost (unless another creature is within 5 ft).

 
I find this interesting. If I have Mirror Image up and you GFB at me and you wind up hitting one of my duplicates, you have still *hit* with that attack. You _had_ to have hit, otherwise the duplicate wouldn't be destroyed. This implies that if you GFB at me and I use a Mirror Image duplicate to absorb the attack, *and* you hit, you could still use the second part of Green-Flame Blade to pop me in the face with fire damage, since the only requirement is that you _hit_ with the attack in order to trigger the secondary effect.

The problem with this comes into effect in the event of you choosing to use the Duplicate after I've declared the Attack. I have to target you with GFB; I can't use it to *intentionally* target a duplicate. So I've already cast the spell; that's happened. If you then roll to determine whether I hit you or your duplicate, I've already targeted *you* with the spell, so I've "made a weapon attack against you." You decided to change the target of my attack to a duplicate of you, but, again, the spell has already been cast, and I've already made the attack roll. It can't be uncast because its target is changed, because the thing that's causing the target changing to happen is the targeting of you with my attack roll, which happens as part of casting the spell. 

What I *intend* to hit versus what I actually wind up hitting is where it kind of gets grey. 

GFB says "On a hit, the target suffers the weapon attack’s normal effects, and you can cause green fire to leap from the target to a different creature of your choice that you can see within 5 feet of it." 

So, the target of the melee attack, which by necessity of me casting it, was you, the creature. That you changed my target to the duplicate is irrelevant, because the only thing that matters for triggering the flame burst is that the target of that attack was hit, and I still have to hit your duplicate. Leaves us with basically a few easy ways to rule: By saying "I cast Green-Flame Blade on the Mirror Image'd Mage," I trigger your Mirror Image response, which you roll and successfully change my target.

1. Because you've changed my target, you've invalidated my spell and it fails. I still had to use my Action to do the thing, so I've basically been bamboozled. (This sucks, in my opinion.)
   
   
2. Even though you've changed my target, I was *trying* to hit you, which is basically what "making an attack against" means, so my spell is valid, but all I can hope to do is destroy your duplicate with a successful attack. (This is ok, probably fair, and I would certainly use this logic for monsters attacking players with Mirror Image up) 
   
   
3. Even though you've changed my target, I was *trying* to hit you, which is basically what "making an attack against" means, so my spell is valid, but after destroying your duplicate with a successful attack, I can have the fire leap to any creature other than you because I had originally targeted you. This would, logically, exclude your duplicates, as they aren't creatures.  (This one seems most legitimate to me, as it seems to honor purpose of both effects.)
   
   
4. Even though you've changed my target, I was *trying* to hit you, which is basically what "making an attack against" means, so my spell is valid, but after destroying your duplicate with a successful attack, I can have the fire leap at you, dealing damage that your duplicates can't absorb because it's not an attack roll. This depends on the idea that the fire must leap from the main target (which became the duplicate) to another target which is not the same target and is also a creature, for which you qualify. (This one is one that I'd only award to players who came up with it as a strategy to counter a Monster with Mirror Image, or a similar effect like a Cloaker. It's super clever and I kind of like the idea of the green flame having a 'disrupting' effect on the illusory defense, narratively.)
   
   
5. Even though you've changed my target, I was *trying* to hit you, which is basically what "making an attack against" means, so my spell is valid, but after destroying your duplicate with a successful attack, I can have the fire leap at you or your duplicate, and if at you, you can choose to have the next duplicate attempt to absorb it, treating it as a separate attack. (There's no reading of the rules that suggest this is valid except Rule of Cool. Again, I might consider it for a player fighting a boss with Mirror Image active, because it's clever. But I would never use it against a player just to burn through their Mirror Images.)

That's a fun edge case scenario. I think the only truly crap ruling are the first and last ones, as they feel like ways you're trying to mess up each other's cool thing. A player making the #1 argument against a DM is just trying to get by on rules cheek, and that's kind of not fun. I might give it to 'em once. A DM arguing #1 against a player (you can't use your spell and your action is wasted) is just saying "you don't play game this turn, lol" and I think that sucks absolute crap. Similarly, a DM making the #5 argument against a player is just trying to take away their Mirror Image defenses, which hard sucks. A player making the #5 argument against the DM is arguably trying to cheese a valid defense away from the DM, which is less sucky than taking agency away from the players.

Ruling #2 is boring but basically fair. Ruling #3 is probably the most fair and is less boring (more stuff happens). Ruling #4 is probably how I'd go if they sold me on it at all. 

....this all also goes away if you use a version of Green-Flame Blade where it's a Bonus Action spell that can trigger when a melee weapon attack deals damage to a creature. That makes it both better for Extra Attack users and more logical for the whole game, which is what I dun did anyway because I got tired of the confusion of the rules for sword-mage cantrips.

Like all good spells its depending on your situation.  But I agree, its not always ideal to run blur when you could take a much better control/heal or even damage spell in that slot which would generally make the success of your party more likely - though in situations when being an ultimate tank blocking a chokepoint then its a reliable way to really help the party succeed.

See the one thing mirror image has going for it (apart from the lack of concentration slot) is that there are many ways to have your enemies have disadvantage on attacks, and it stacks with all of those.  Multiple sources of disadvantage don't stack.

I love my gishes to stack different forms of defence, in particular I usually take blindfighting when taking one of my martial levels (fighter/ranger/pal) as it opens up LOTS of ways to ensure you are fighting with advantage and/or enemies at disadvantage.  I also love ensuring I have the three groovy stacks of defence - mirror image, aid, and some form of temp hp (armor of agatha if you can get it!), all of these things can give you a real boost and don't have the downside of potentially rolling a bad concentration save and losing them all.

I see people arguing to choose mirror image or Blur, and I say..why not both?

Both

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An enemy using green flame blade certainly doesn't mind your mirror image spell. There's a non-zero chance your duplicates are easier to hit than you are, so rolling against your duplicate gives a GFB fighter the opportunity to still splash damage on you. 

I think they're situationally relevant. A blur could protect from Sneak Attack-style damage and other such riders for slightly longer; even if the attacks hit, simply forcing them to be made with disadvantage has its purpose. 

 Correct me if I'm wrong, but I believe GFB would not work. GFB requires that you target a creature, meaning you have to target the caster, not a duplicate. And because a duplicate is not a creature, if you miss the caster adn hit a dupe, GFB would not leap over to the caster.

 “Creature” is a very broad term.

In this context, I would rule that the attacker perceives the illusion as a creature, and so they would still be able to target and hit it, hitting you with splash damage.

 

You're obviously free to rule that way at your table, but that's not how GFB or Mirror Image work RAW.

Illusions are not creatures unless explicitly stated as such. They aren't in this case. And there are good reasons for that. Like mentioned above they aren't affected by AOE. If they were creatures though, they would be. But what would their save bonus be? How much hp do they have? They have no stats. They could be targeted by other spells as well if they were creatures. Etc. Treating them as creatures raises a bunch of questions with no answers because they quite clearly are not meant to be treated as creatures.

Furthermore, the whole point of Mirror Image is the attacker doesn't know which one is real. So you can't choose to target a copy any more than you can choose to target the real creature (which again, would become untrue if the copies were creatures). You make an attack and it hits one of them randomly, and the GFB secondary damage is lost (unless another creature is within 5 ft).

 
I find this interesting. If I have Mirror Image up and you GFB at me and you wind up hitting one of my duplicates, you have still *hit* with that attack. You _had_ to have hit, otherwise the duplicate wouldn't be destroyed. This implies that if you GFB at me and I use a Mirror Image duplicate to absorb the attack, *and* you hit, you could still use the second part of Green-Flame Blade to pop me in the face with fire damage, since the only requirement is that you _hit_ with the attack in order to trigger the secondary effect.

The problem with this comes into effect in the event of you choosing to use the Duplicate after I've declared the Attack. I have to target you with GFB; I can't use it to *intentionally* target a duplicate. So I've already cast the spell; that's happened. If you then roll to determine whether I hit you or your duplicate, I've already targeted *you* with the spell, so I've "made a weapon attack against you." You decided to change the target of my attack to a duplicate of you, but, again, the spell has already been cast, and I've already made the attack roll. It can't be uncast because its target is changed, because the thing that's causing the target changing to happen is the targeting of you with my attack roll, which happens as part of casting the spell. 

What I *intend* to hit versus what I actually wind up hitting is where it kind of gets grey. 

GFB says "On a hit, the target suffers the weapon attack’s normal effects, and you can cause green fire to leap from the target to a different creature of your choice that you can see within 5 feet of it." 

So, the target of the melee attack, which by necessity of me casting it, was you, the creature. That you changed my target to the duplicate is irrelevant, because the only thing that matters for triggering the flame burst is that the target of that attack was hit, and I still have to hit your duplicate. Leaves us with basically a few easy ways to rule: By saying "I cast Green-Flame Blade on the Mirror Image'd Mage," I trigger your Mirror Image response, which you roll and successfully change my target.

1. Because you've changed my target, you've invalidated my spell and it fails. I still had to use my Action to do the thing, so I've basically been bamboozled. (This sucks, in my opinion.)
   
   
2. Even though you've changed my target, I was *trying* to hit you, which is basically what "making an attack against" means, so my spell is valid, but all I can hope to do is destroy your duplicate with a successful attack. (This is ok, probably fair, and I would certainly use this logic for monsters attacking players with Mirror Image up) 
   
   
3. Even though you've changed my target, I was *trying* to hit you, which is basically what "making an attack against" means, so my spell is valid, but after destroying your duplicate with a successful attack, I can have the fire leap to any creature other than you because I had originally targeted you. This would, logically, exclude your duplicates, as they aren't creatures.  (This one seems most legitimate to me, as it seems to honor purpose of both effects.)
   
   
4. Even though you've changed my target, I was *trying* to hit you, which is basically what "making an attack against" means, so my spell is valid, but after destroying your duplicate with a successful attack, I can have the fire leap at you, dealing damage that your duplicates can't absorb because it's not an attack roll. This depends on the idea that the fire must leap from the main target (which became the duplicate) to another target which is not the same target and is also a creature, for which you qualify. (This one is one that I'd only award to players who came up with it as a strategy to counter a Monster with Mirror Image, or a similar effect like a Cloaker. It's super clever and I kind of like the idea of the green flame having a 'disrupting' effect on the illusory defense, narratively.)
   
   
5. Even though you've changed my target, I was *trying* to hit you, which is basically what "making an attack against" means, so my spell is valid, but after destroying your duplicate with a successful attack, I can have the fire leap at you or your duplicate, and if at you, you can choose to have the next duplicate attempt to absorb it, treating it as a separate attack. (There's no reading of the rules that suggest this is valid except Rule of Cool. Again, I might consider it for a player fighting a boss with Mirror Image active, because it's clever. But I would never use it against a player just to burn through their Mirror Images.)

 

That's a fun edge case scenario. I think the only truly crap ruling are the first and last ones, as they feel like ways you're trying to mess up each other's cool thing. A player making the #1 argument against a DM is just trying to get by on rules cheek, and that's kind of not fun. I might give it to 'em once. A DM arguing #1 against a player (you can't use your spell and your action is wasted) is just saying "you don't play game this turn, lol" and I think that sucks absolute crap. Similarly, a DM making the #5 argument against a player is just trying to take away their Mirror Image defenses, which hard sucks. A player making the #5 argument against the DM is arguably trying to cheese a valid defense away from the DM, which is less sucky than taking agency away from the players.

Ruling #2 is boring but basically fair. Ruling #3 is probably the most fair and is less boring (more stuff happens). Ruling #4 is probably how I'd go if they sold me on it at all. 

 

....this all also goes away if you use a version of Green-Flame Blade where it's a Bonus Action spell that can trigger when a melee weapon attack deals damage to a creature. That makes it both better for Extra Attack users and more logical for the whole game, which is what I dun did anyway because I got tired of the confusion of the rules for sword-mage cantrips.

My dude you are typing way too much for an obvious answer to this question

> "On a hit, the target suffers the weapon attack’s normal effects, and you can cause green fire to leap from the target to a different creature of your choice that you can see within 5 feet of it." 

>from the target to a different creature

>different creature

>different

Mirror Images don't count as different creatures. It's a magical effect.

It's not that complicated.

All these posts begs the question: Does the Blind Fighting fighting style negate Blur since anyone using that fighting style isn't relying on their sight?

My knee-jerk decision is "yes" but I wanted to see if anyone has a logical argument against that decision.

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All these posts begs the question: Does the Blind Fighting fighting style negate Blur since anyone using that fighting style isn't relying on their sight?

My knee-jerk decision is "yes" but I wanted to see if anyone has a logical argument against that decision.

Yes. The Blind Fighting fighting style says that it gives you blindsight with a radius of 10 feet, and this spell explicitly says that an attacker is immune to it if it has blindsight. 

It isn't completely negated, though, as the fighting style's blindsight only has a radius of 10 feet. The attacker with Blind Fighting would still be subject to this spell's effects if attacking from beyond 10 feet with a ranged attack.