Mirror Image Math

Worrgrendel

Explorer
I guess your DM doesn't use dispel magic alot.

This PC could go from hero to zero very quickly.
Hit with dispel magic AC goes from potentially 28 to 23 with Shield. Nothing to sneeze at at level 9. Plus there is always Counterspell if reaction still available. As soon as +1 Studded Leather is found then the Mage Armor issue is negated and AC only drops to 26 with Shield. I don't see Dispel Magic as a Hero to Zero issue.
 
Hit with dispel magic AC goes from potentially 28 to 23 with Shield. Nothing to sneeze at at level 9. Plus there is always Counterspell if reaction still available. As soon as +1 Studded Leather is found then the Mage Armor issue is negated and AC only drops to 26 with Shield. I don't see Dispel Magic as a Hero to Zero issue.
They would be stripped of shield, mage armor, and haste on top of being stunned due to haste dropping which would also kill bladesong.
can't shield and CS same round so if they are the only one with CS and they pop shield it's pretty bad.
Dispel magic has a much longer range than CS which is something that gets overlooked alot.
 
They would be stripped of shield, mage armor, and haste on top of being stunned due to haste dropping which would also kill bladesong.
can't shield and CS same round so if they are the only one with CS and they pop shield it's pretty bad.
Dispel magic has a much longer range than CS which is something that gets overlooked alot.
Maybe I am looking at an older version of the Bladesinging tradition but what I read says it ends if you are incapacitated, don medium/heavy armor or shield, or use 2 hands to make an attack. When haste ends you can't move or take actions until after your next turn. I don't see a conflict with bladesong staying up and haste ending.

Losing 10 ac though is still brutal, I agree. I find it amusing to drop dispel magic on a blade singer and watch them freak out if they are hip deep in enemies who get a turn to try to beat them down without crazy ac.
 
Maybe I am looking at an older version of the Bladesinging tradition but what I read says it ends if you are incapacitated, don medium/heavy armor or shield, or use 2 hands to make an attack. When haste ends you can't move or take actions until after your next turn. I don't see a conflict with bladesong staying up and haste ending.

Losing 10 ac though is still brutal, I agree. I find it amusing to drop dispel magic on a blade singer and watch them freak out if they are hip deep in enemies who get a turn to try to beat them down without crazy ac.
No I was wrong actually. I was remembering haste wrong so blade song would stay up. Not as bad as I first thought. Still would be a big blow to the bladesinger's defense and action economy.
 

Worrgrendel

Explorer
They would be stripped of shield, mage armor, and haste on top of being stunned due to haste dropping which would also kill bladesong.
can't shield and CS same round so if they are the only one with CS and they pop shield it's pretty bad.
Dispel magic has a much longer range than CS which is something that gets overlooked alot.
Lucas already pointed out that Bladesong would still be up so we can skip over that.

Most fights do not involve casters. I realize that can also be campaign dependent. To further that, not all caster mobs have Dispel Magic. Additionally, its not hard to figure out whether or not a mob is a caster and my wife is smart enough to figure out if there is a caster on the table then that reaction is held for Counterspell and not Shield. Without Shield available her AC is still good and can weather most attacks, even if she is surrounded and especially if Mirror Image is up. As to the range of Dispel Magic vs Counterspell, how many fights open up at 120 feet? or 90 feet? If the DM wants his caster to spam Dispel Magic at the Bladesinger I feel that to be a waste of the caster's actions while the 5 other party members are completely ignored and burn him/her to the ground.

YMMV
 

Worrgrendel

Explorer
If one is fighting Drow, all of them.
So you fight nothing but Drow in all of your campaigns and every encounter in the Underdark is a room that is larger than 120 feet across and they all automatically know to target Dispel Magic on one exact member of the group? That seems a bit niche. There are a plethora of good adventures out there by WOTC and 3rd party DM's Guild that do not take place solely in the Underdark. I recommend a change of pace for your gaming group and have them "step outside" for your next campaign for a little variety. Maybe something with Dragons or a Death Curse or a Vampire lord or even Hell?
 

Todd Roybark

Adventurer
LOL, and for you @Worrgrendel, I recommend some encounters with opponents using Longbows at 600’ range.🏹

I presume you are being humorous with a bit of snark, but many creatures have some long range ability. Beholderkin 👁 being a prime example.
 
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Esker

Hero
I think it might be helpful to work backwards...

Let C(n,m) be your expected number of hits with n attacks to come if you have m images remaining. Then (assuming for simplicity that we pre-cast MI) we are interested in C(n,3) as compared to C(n,0).

Let T(m) be the chance that an image is targeted when you have m of them, and let x and y be as you defined them in the OP. We have T(0) = 0, T(1) = 10/20, T(2) = 13/20, T(3) = 15/20.

Then

C(n,0) = nx

C(1,m) = (1 - T(m)) * x

and for m > 0 and n > 1:

C(n,m) = C(1,m) + (1 - T(m) + T(m)*(1-y)) * C(n-1,m) + T(m) * y * C(n-1,m-1)
 

Saelorn

Hero
Why are you assuming that anyone would see a Mirror Image, and respond by making normal attacks against it? Isn't that playing right into their plan?

I always figured that this spell, much like any source of Disadvantage, works primarily by disincentivizing the enemy from attacking you in the first place. The ogre isn't going to risk wasting a big swing on something it probably can't hit, but the kobolds who have numbers on their side will spend their attacks because they're contributing toward the goal of making you hittable.
 

Dausuul

Legend
The ogre isn't going to risk wasting a big swing on something it probably can't hit, but the kobolds who have numbers on their side will spend their attacks because they're contributing toward the goal of making you hittable.
Because ogres and kobolds are known for their tactical savvy and their extensive knowledge of arcane magic?
 

Saelorn

Hero
Because ogres and kobolds are known for their tactical savvy and their extensive knowledge of arcane magic?
If we're assuming that someone with magic is fighting ogres and kobolds, then we can assume that ogres and kobolds are known to fight people who have magic.
 

Dausuul

Legend
If we're assuming that someone with magic is fighting ogres and kobolds, then we can assume that ogres and kobolds are known to fight people who have magic.
Sure, maybe the ogre smashed a cleric once or the kobolds ambushed a sleeping wizard. That's very different from recognizing a specific spell, understanding its limitations and effects, and using the optimal counter-tactic.
 

doctorbadwolf

Heretic of The Seventh Circle
Well - not my goal but useful info.

I've calculated Blur's damage reduction for the nth attack coming at you.

Let C = Chance Concentration remains up through hit < 21 damage. X = Chance to be hit. N = Number of attacks. Then,

X - C^N * (X-X^2)

Unless you have extremely high concentration then blur actually loses value pretty quickly the more attacks come at you.

Someone else double check my work on this one!
Blur definitely gets better for someone like a Bladesinger with Warcaster. Even with a 13 con and 16 int, my Bladesinger almost never loses concentration.

Already high AC also means disadvantage attacks nearly never hit, because you need such a high die roll. In basic terms with low AC Blur is fishing for low rolls on the defensive side, while with high AC you force the enemy to fish for two higher than average rolls.

Mirror Image, OTOH, relies less on anything other than the spell itself to protect you. Not something that is easy to quantify, but certainly a benefit.
 

Saelorn

Hero
Sure, maybe the ogre smashed a cleric once or the kobolds ambushed a sleeping wizard. That's very different from recognizing a specific spell, understanding its limitations and effects, and using the optimal counter-tactic.
If you insist on playing your monsters as clueless, then replace the example with humanoids. A barbarian (or knight) still isn't going to waste a big swing, if there's an 80% chance of missing, and there are other targets available.

You should never assume that the enemy is clueless. That's not a factor that you control, and relying on it will give you theoretical data that doesn't hold up in practice.
 

doctorbadwolf

Heretic of The Seventh Circle
Because ogres and kobolds are known for their tactical savvy and their extensive knowledge of arcane magic?
I don’t think that really requires much intelligence. The magic guy just made himself into 4 people, and it’s hard to tell what’s real. I hit slow and big, and the guy with the shield is just standing there.

It’s not advanced tactics.
 
Sure, maybe the ogre smashed a cleric once or the kobolds ambushed a sleeping wizard. That's very different from recognizing a specific spell, understanding its limitations and effects, and using the optimal counter-tactic.
Mirror Image is one of the most common defensive spells used by wizards - it's even common in movies, it's one of MCU Loki's go-to spells, amongst other examples - and pretty much every wizard in Baldur's Gate CRPG casts it first. Unless it's a very low magic setting even fairly unintelligent foes are going to learn how to handle it.
 
If you insist on playing your monsters as clueless, then replace the example with humanoids. A barbarian (or knight) still isn't going to waste a big swing, if there's an 80% chance of missing, and there are other targets available.

You should never assume that the enemy is clueless. That's not a factor that you control, and relying on it will give you theoretical data that doesn't hold up in practice.
likewise you should never assume the enemy has a clue.
 

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