Is Blur or Mirror Image better in D&D 5e?

Calculating which defensive spells is best.

Rules and changes

Blur

First off, let’s take a look at blur. Below are the 2014 rules for this spell

2nd Level illusion

Casting Time: action
Range: self
Components: V
Duration: 1 minute, concentration

Your body becomes blurred, shifting and wavering to all who can see you. For the duration, any creature has disadvantage on attack rolls against you. An attacker is immune to this effect if it doesn’t rely on sight, as with blindsight, or can see through illusions, as with truesight.

Available for: Artificer, sorcerer, wizard

PHB 2014, p219

Although there are some wording changes in the 2024 version, the effects of the spell remain exactly the same.

Essentially, you cause all attackers to have disadvantage on attack rolls against you unless they have blindsight or truesight. It’s worth noting that this spell will occupy your concentration.

Mirror image

Now let’s take a look at mirror image. below are the 2014 rules:

2nd Level illusion

Casting Time: action
Range: self
Components: V, S
Duration: 1 minute

Three illusory duplicates of yourself appear in your space. Until the spell ends, the duplicates move with you and mimic your actions, shifting position so it’s impossible to track which image is real. You can use your action to dismiss the illusory duplicates.

Each time a creature targets you with an attack during the spell’s duration, roll a d20 to determine whether the attack instead targets one of your duplicates.

If you have three duplicates, you must roll a 6 or higher to change the attack’s target to a duplicate. With two duplicates, you must roll an 8 or higher. With one duplicate, you must roll an 11 or higher.

A duplicate’s AC equals 10 + your Dexterity modifier. If an attack hits a duplicate, the duplicate is destroyed. A duplicate can be destroyed only by an attack that hits it. It ignores all other damage and effects. The spell ends when all three duplicates are destroyed.

A creature is unaffected by this spell if it can’t see, if it relies on senses other than sight, such as blindsight, or if it can perceive illusions as false, as with truesight.

Available for: Sorcerer, Warlock, wizard

PHB 2014, p260

Essentially, you create 3 illusory copies of yourself, giving a chance for attacks against you to strike an illusory copy and save you from the damage. It’s worth noting that unlike blur, mirror image doesn’t require concentration.

The 2024 version does change things up a fair bit:

2nd Level illusion

Casting Time: action
Range: self
Components: V, S
Duration: 1 minute

Three illusory duplicates of yourself appear in your space. Until the spell ends, the duplicates move with you and mimic your actions, shifting position so it’s impossible to track which image is real.

Each time a creature hits you with an attack roll during the spell’s duration, roll a d6 for each of your remaining duplicates. If any of the d6s rolls a 3 or higher, one of the duplicates is hit instead of you, and the duplicate is destroyed. The duplicates otherwise ignore all other damage and effects. The spell ends when all three duplicates are destroyed.

A creature is unaffected by this spell if it has the Blinded condition, Blindsight, or Truesight.

Available for: Bard, sorcerer, warlock, wizard

PHB 2024, p299

The big change is how hitting an illusion is calculated. Now you roll a d6 for each illusory copy and one is hit if you roll a 3 or higher. This is a 66% chance on each die, so 96% with 3 illusions, 89% with 2 and 66% with 1. In the 2014 rules, the odds are 75% with 3 illusions, 60% with 2 and 50% with one.

Immediately, it’s obvious that the odds of an illusion being hit have increased. The other big change is that the 2024 version of the spell only triggers if you are hit by the attacker. The 2014 version determines who is targeted and then works out the AC of the illusory copies based on what is the lowest possible AC you might have (10 + your dexterity modifier). This means illusions were more likely to be wasted on attacks that wouldn’t have hit anyway in the 2014 version (and the process was slower).

A couple of other minor changes include the fact that this spell doesn’t affect creatures with the blinded condition (so an enemy could cast darkness on you both to not be affected by your mirror image for example). It’s also now available to bards too.

Analysing the effectiveness of each spell

To help us here, I’ve put together a good old pros and cons list (or 2):

I would say that mirror image tends to be more reliable, but has less potential for protecting you from many attacks. This is especially the case for melee characters that will want to dive into combat and expect to be attacked often (like Eldritch Knights or blade Warlocks).

With mirror image being limited to helping against no more than 3 attacks, these characters may find they get less use out of mirror image. The 2024 version does improve things here a bit by not wasting some of those illusions on attacks that wouldn’t have hit you anyway.

Blur, on the other hand, can last a whole combat if you can maintain concentration. This makes it better for characters that expect to be attacked a lot and that likely won’t need their concentration on something else (often this will be martial spellcasters).

You can see the impact a bit more clearly in the table below. It calculates odds to hit you based on your AC and the attacker’s bonus to hit. The first number in each cell is the odds without blur active and the 2nd number is with blur active.

AC	+2	+3	+4	+5	+6	+7	+8	+9	+10	+11	+12	+13	+14
12	55%/30%	60%/36%	65%/42%	70%/49%	75%/56%	80%/64%	85%/72%	90%/81%	95%/90%	95%/90%	95%/90%	95%/90%	95%/90%
13	50%/25%	55%/30%	60%/36%	65%/42%	70%/49%	75%/56%	80%/64%	85%/72%	90%/81%	95%/90%	95%/90%	95%/90%	95%/90%
14	45%/20%	50%/25%	55%/30%	60%/36%	65%/42%	70%/49%	75%/56%	80%/64%	85%/72%	90%/81%	95%/90%	95%/90%	95%/90%
15	40%/16%	45%/20%	50%/25%	55%/30%	60%/36%	65%/42%	70%/49%	75%/56%	80%/64%	85%/72%	90%/81%	95%/90%	95%/90%
16	35%/12%	40%/16%	45%/20%	50%/25%	55%/30%	60%/36%	65%/42%	70%/49%	75%/56%	80%/64%	85%/72%	90%/81%	95%/90%
17	30%/9%	35%/12%	40%/16%	45%/20%	50%/25%	55%/30%	60%/36%	65%/42%	70%/49%	75%/56%	80%/64%	85%/72%	90%/81%
18	25%/6%	30%/9%	35%/12%	40%/16%	45%/20%	50%/25%	55%/30%	60%/36%	65%/42%	70%/49%	75%/56%	80%/64%	85%/72%
19	20%/4%	25%/6%	30%/9%	35%/12%	40%/16%	45%/20%	50%/25%	55%/30%	60%/36%	65%/42%	70%/49%	75%/56%	80%/74%
20	15%/2%	20%/4%	25%/6%	30%/9%	35%/12%	40%/16%	45%/20%	50%/25%	55%/30%	60%/36%	65%/42%	70%/49%	75%/56%
21	10%/1%	15%/2%	20%/4%	25%/6%	30%/9%	35%/12%	40%/16%	45%/20%	50%/25%	55%/30%	60%/36%	65%/42%	70%/49%
22	5%/0.25%	10%/1%	15%/2%	20%/4%	25%/6%	30%/9%	35%/12%	40%/16%	45%/20%	50%/25%	55%/30%	60%/36%	65%/42%

The big thing to note is that with a higher AC, the effects of blur tend to be more substantial. This again favours martial characters.

So which spell is better?

Blur is a more potent spell because it will aid against more attacks, unless you expect to get attacked infrequently, in which case, mirror image is more potent, working 66-96% of the time. But it will only be potent 3 times.

It’s also worth noting that creatures with a high hit bonus will feel the effects of disadvantage less, making mirror image more potent against very high CR creatures.

With blur requiring concentration too, I’d tend to recommend it for martials who expect to be attacked a lot, are likely to have a higher AC and don’t need to use concentration spells on other things.

For mirror image, I’d tend to recommend it for characters with a lower AC, that tend to get attacked less and need their concentration on other spells.

Essentially, neither is necessarily better than the other, but instead, each is just better in different circumstances.

How to get mirror image and blur

The easiest way to get these spells is through your class’ spell list. The following class’ have access to each spell:

Blur: Artificer, sorcerer, wizard, circle of the land druid, hexblade warlock, the genie warlock

Mirror image: Bard (2024 only), sorcerer, warlock, wizard, trickery domain cleric (2014 only), circle of the land druid, armorer artificer

The other way to grab these spells is through the fey touched feat as they’re both illusion spells.

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What do you think of blur and mirror image, and which do you prefer to use? Let me know in the comments below.

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