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Some context: We're running Dragon Heist and the party is brainstorming on a smart combo game plan to fight the Xanathar himself. In this question I've clarified why in our encounter and generally it may not always be reasonable for a Beholder to point the Antimagic Cone at the target instead of shooting his rays at with a readied action (even if that target is a spellcaster, there is always a tradeoff: "disable magic VS just kill that thing"). So here the party started to brainstorm on some smart ways to buff themselves against the Beholder's rays.

One of the proposed tactics was to cast Mirror Image. I thought this was a cool idea! But then I read the description of the spell again and then stumbled upon this question where the consensus is that Mirror Image only protects against the effects that specifically mention "attack" in their description.

So it seems that, according to the rules, the Mirror Image is completely useless against the Beholder's rays. Because just like the disintegrate spell, the disintegrate ray is not an "attack".

But how in the world should I explain that to my players? 🤷‍♀️

When reading the Mirror Image spell description, here is what I imagine (it's a screenshot from a video game Baldur's Gate 2, based on D&D): Mirror image from Baldurs Gate Actually, I even remember playing Icewind Dale / Baldur's Gate video games and remember that when I casted Mirror Image, it always looked like there are identical duplicates, indistinguishable from each other, just like the spell states:

duplicates move with you and mimic your actions, shifting position so it's impossible to track which image is real.

Other spell lore like this one also suggests that those images are identical.

So how would my Beholder know which one of the images is the real target? Is it because he's super smart or something? What about spellcasters?

I honestly don't know how to explain it to my party. I'm one step away from saying "this is a HUGE hole in the D&D rules and I'm house-ruling this spell: the Beholder now will have to roll d20 and there's a chance he'll waste one of his rays at one of the illusory doubles". Wouldn't that make Mirror Image overpowered then?

But maybe I'm missing something and there is a nice way to explain the rationale behind Mirror Image not working against the Beholder's rays (as well as against the spells that are targeted at a creature but don't have "attack" in their description)?

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8 Answers 8

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The Beholder rays replicate effects from spells requiring saving throws and not attack rolls.

The rays of the Beholder replicate the effect of spells that affect the target(s) after a unsuccessful saving throw:

  1. Charm Ray replicates Charme.
  2. Paralyzing Ray replicates Hold Monster.
  3. Fear Ray replicates Fear.
  4. Slowing Ray replicates Slow.
  5. Enervation Ray replicates Enervation.
  6. Telekinetic Ray replicates Telekinesis.
  7. Sleep Ray replicates Sleep.
  8. Petrification Ray replicates Flesh to Stone.
  9. Disintegration Ray replicates Disintegrate.
  10. Death Ray replicates some effects from Finger of Death.

All the above spells do not require attack rolls: they are successful if the target(s) fail the saving throw. Moreover, some of them have the requirement to be able to see the target(s), which kind of make sense for a magical ray fired from an eye of a beholder.

The BG2 image is misleading.

Pay attention that the image from BG2 is misleading\$^\dagger\$, the game uses the ADnD 2nd edition rules and spells, in such edition Mirror Image has an AoE of 6 ft. radius. In the 5th edition version the spell's description says

Three illusory duplicates of yourself appear in your space

meaning that they are in the same position of the caster (a square of 5ft square if you are using a tactical map).

This means that a creature, protected by the Mirror Image spell, in the AoE of a Beholder's ray is affected by the ray, as well as all their duplicates, because they stand in the same space.


Mirror Image protects\$^\ddagger\$ against attacks because the caster is switching position with their duplicates: since an attack targets only one target, the spell gives a chance that the actual target of the attack is one of the duplicates and not the caster.

For AoE effects (such as spells like Fireball), since the creatures and their duplicates occupy the same space, all of them are in the AoE, in particular the caster. The duplicates are not affected because the spell says so:

A duplicate can be destroyed only by an attack that hits it. It ignores all other damage and effects.

You are the DM: you can houserule as it better suits to your table.

But why the beholder's ray cannot affect the duplicates? Because the rules say so: they are not attacks. If it feels an unsatisfactory answer (and it is), you can come up with a (more or less) reasonable explanation: for example, the beholder's ray is so thick that covers all the space occupied by the caster and their duplicates. As a DM, you can find an explanation that suits your table, with a reasonable amount of suspension of disbelief.

Obviously, if you like the BG2 depiction of the spell you are completely free to employ it in your games. As you noted, this will lead to adjust the interactions with other game features.


\$^\dagger\$ In the latest version of BG, BG2, IWD and IWD2 the Mirror Image gathered all the duplicates around the caster, see here for example.

\$^\ddagger\$ Why the spell acts in this way? We should ask to the original inventor of this, the Netherese Arcanist Smolyn.

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  • \$\begingroup\$ Minor note, Baldur's Gate is based on much older edition. Then, images appeared anywhere in 6 foot radius, so by today's standards line 3 squares long wasn't out of the question. But spell was working with space rules that were in use then, not the ones we have now. \$\endgroup\$
    – Mołot
    Nov 15, 2022 at 7:26
  • \$\begingroup\$ @Mołot Right, I forgot to provide more detail about the spell in BG2, which indeed is based on the 2nd edition of ADND. I will do it asap. \$\endgroup\$
    – Eddymage
    Nov 15, 2022 at 7:56
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    \$\begingroup\$ Also, in earlier editions, a beholder's eye rays did actually require attack rolls or the edition-specific equivalent. \$\endgroup\$
    – GMJoe
    Feb 12, 2023 at 0:46
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You are the DM; It is your game, your rules.

If the common understanding of a rule or interaction of rules differ from the understanding of yourself and your group, you can make whichever call suits your understanding the most. Don't feel bad about going against the online consensus; feel free, however, to discuss the controversy with your group, so they know you are making a ruling.

Explaining the exception

My understanding is that Mirror Image is illusions moving very close to you, not as you depicted them in a rather long line. They make exact aim hard, while still leaving you vulnerable to area effects (e.g. Stinking Cloud).

To the best of my understanding, Beholder Rays are directed, not aimed, and have a somewhat wider area than the stereotypical "laser beam". That is, they constitute area effects, and as long as you are "approximately" where they are aiming (i.e., in the "same space", as Mirror Image puts it), you will be hit.

Note, however...

Most Ray spells, unlike Beholder Rays, do require an attack roll.

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    \$\begingroup\$ I like this, the beholder swipes the whole (tiny) area with the ray and it catches the player while leaving the mirrors unaffected. \$\endgroup\$
    – SeriousBri
    Nov 8, 2022 at 16:09
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    \$\begingroup\$ I would be careful calling it an area effect. An eye-ray targets a creature, not an area, but otherwise your answer is correct -- like acid splash or frostbite, the eye-ray just kinda bursts somewhere close to the target and affects them, and it's down to the target's ability to dodge, resist, or otherwise avoid the effect. \$\endgroup\$ Nov 8, 2022 at 17:16
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    \$\begingroup\$ It's worth noting that magic missiles specifically do not require an attack roll and are not treated as an "attack roll that automatically hits." They are specifically ineffective on mirror images, unless you're using the AI variant "Jim's Magic Missle" which does make an attack roll. Rule Zero obviously applies, but it's not an explanation I'd float to my players while trying to explain why the eye rays don't work. \$\endgroup\$ Nov 8, 2022 at 17:46
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    \$\begingroup\$ Don't feel bad about going against the online consensus +1 \$\endgroup\$
    – Wyrmwood
    Nov 8, 2022 at 22:31
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    \$\begingroup\$ I would rule the Beholder directs a "concentrated" ray against one target (say the closest). If it sees the target is an illusion, it grumbles in frustration and will shoot all the mirror images with a less potent ray if Mirror Image is cast again. \$\endgroup\$
    – RobertF
    Nov 9, 2022 at 15:26
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Numb yourself to the disconnect with reality

This is just one of countless incongruences we have to live with playing D&D. You also do not accelerate when falling, fireballs do not evaporate water, attacks can beat you within inches of dying with no effect whatsoever on your ability to function, creatures caught in a web in flight plummet to the ground, you can run 30 feet in full armor, summon a spiritual weapon, attack, and retrieve something from your backback, all in six seconds, all your wounds heal overnight, and two blind archers hit each other just as well as if they would be seeing. We are just numb to most of these weirdnesses because we got so used to them that they do not register any more.

There is a reason that D&D is not a physics simulation: playability. So, sure you could try and work around with homebrew rules, or contrive a justification. But much simpler is to accept it is just a game, suspend disbelief, and soon enough you'll not think about it any more. Just like all the other stuff.

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  • \$\begingroup\$ Why would a flying creature caught in a web falling be not realistic? (or is this my numbness showing) \$\endgroup\$
    – justhalf
    Nov 9, 2022 at 2:39
  • \$\begingroup\$ @justhalf What happens to a fly caught in a web in real life? The web has to be anchored. \$\endgroup\$ Nov 9, 2022 at 4:41
  • \$\begingroup\$ I was imagining the web is thick enough to stop wings from moving \$\endgroup\$
    – justhalf
    Nov 9, 2022 at 5:07
  • \$\begingroup\$ @justhalf I think my point is that you are *stuck in a web•, so it does not matter if you can fly or not any more — because you are stuck. You cannot move any more. You don's see a lot of flies falling to the floor when they get stuck in a web either, because they are stuck \$\endgroup\$ Nov 9, 2022 at 5:14
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    \$\begingroup\$ That's because the web is anchored, right? Probably I was imagining the wrong mental image, as I was thinking of the web being not anchored, so like a net being thrown to capture birds, but in the form of web. \$\endgroup\$
    – justhalf
    Nov 9, 2022 at 5:58
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This is the sort of exception you can only explain via the rules.

The rules for what constitute an attack are simple - via JC during his tenure where it counted, "An attack involves an attack roll or doing something that the rules call an attack, like grappling or shoving. "

These eye rays are not called attacks, and they do not make attack rolls or use an "attack action."

If your party members point out that it still doesn't 'make sense,' ask them if it makes sense that the beholder can't re-orient its antimagic cone on each of its movement actions instead of just at the start of its turn- and then ask if they want it re-orienting the cone multiple times per round.

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    \$\begingroup\$ ...or that beholders even exist in the first place. :) \$\endgroup\$
    – Senmurv
    Nov 8, 2022 at 20:36
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There is no objective answer with this interpretation of the spell.

The issue is the following : you have a spell that says that it allows you to possibly evade attacks, but otherwise ignores other effects, such as the beams you mention. Outside of any explanation in terms of "how would this work with logic?", this is how the spell works.

The problem is the following : magic doesn't follow our world's logic, and we cannot compare it accurately with our world since it doesn't exist. The best we can do is use our own interpretation to give it shape in a way that works in our view of the world.

So here's the situation with Mirror Image. The most common way of representing its effects is saying that when the enemy makes an attack aimed at you, it has to aim it at one of the images, and that's why the spell can make those attacks miss. Another variant is that you can swap your position with said images.

The issue with those interpretations is that some manually targeted effects can ignore those images and go straight for the caster, simply because they're not considered as an "attack". Similarly, according to the rules of the spell, an area-of-effect such as Fireball will ignore the clones, although this logic would dictate that they would be hit and destroyed.

So we're in the situation where we have an interpretation of how Mirror Image works, but that isn't accurate for all situations. This means that this interpretation of the spell is wrong. Or at least, it doesn't satisfy the main point of using an interpretation, and not simply saying "this is the rules" : immersion. In which case, there are two ways to remedy to this :

  • Create a new interpretation : throw away the "mistargetting" interpretation of how this spell works, and explain what it does in another way. In this solution, the most simple way to put it is "The spell does what it says, so let's try to find a proper explanation as to why it does that." Any explanation that satisfies you and your players is a good explanation. This solution makes sure that you keep the current rules and their balance, but can challenge your player's imagination.
  • Change the rules : keep the interpretation that seems logical and adapt the rules of the spell in order for it to fit this view of the spell. In this case, you could houserule that the beam can be affected by the spell's effect, or, taking the Fireball example from before, that such an area of effect will hit and destroy all images at once. While this may be the easiest in the short term, it may have effects on other mechanics of your game later on, or even in the current fight.

There is no better solution. The first one is a challenge for keeping the immersion, while the second one is a challenge for keeping the balance of the game.

To put it shortly : since we can't explain precisely how magic works, the best we can do is create interpretations that fit the rules and our imagination of the scene. If such an interpretation doesn't fit the rules, you'll have to change one or the other. This also means that any "solution" is purely subjective and up to each person's interpretation of the spell.

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What arguments you could make to your players?

One might start by telling the players that no matter how related the tabletop and the video games are, they still are distinct games. What works on one does not translate exactly onto another. Game designers do try to be faithful to the original product but they are known to take liberties.

Second, the "mirror" part on the spell name is a kind of a misnomer. The thing is more like a Kaleidoscope. All the copies are on the same 5x5 square, doing the same action, displaced by less than five feet from one another, and crossing one another. They are shuffling around, enough to make an attack miss, but not enough to spill into another space. Think of those multi-armed dance illusions, or just superimposed images.

Third, an important notion when regarding 5e rules: They do exactly what they say, no more, no less. There are no "fluff" words in the game. If mirror image says it protects against "attacks", then you are out of luck regarding anything that is not an "attack". Case in point, beholder rays.

Even real world lasers need to stay on target for a while to cause an effect. The beholder ray is not a videogame beam that is more like a cilinder of glowing "effect" that travels at fast speeds but still conveniently slow enough to be visually pleasant. Perhaps the ray is a beam that stays on long enough to scour the space. Regardless of how we want to picture it, the game effect is that it targets a creature, creature makes a saving throw.

Now, contrast mirror image with invisibility. If the beholder had to shoot a eye ray/beam at an invisible target, they would need to guess a space like anyone else targeting an effect against an invisible foe they cannot detect or pinpoint. Obviously, if we follow the rules for targeting an invisible enemy, we see that aiming at the correct space is enough to allow the action to proceed.

The conclusion is that mirror image is not lesser than invisibility but conveys a different, more specialized sort of protection. Against stuff that requires an attack roll. The beholder's rays/beams don't.

Bottom line, I'll borrow a strategy from FASA:

Say it to them straight:

Guys, I think we got Mirror Image wrong. It's not like the video game. See, it says here (show them the spell description) that it protects only against attacks, when we roll to hit against the target's armor class. The beholder rays require saving throws, not attack rolls.

So, how do you think we should move on? Should we allow the spell to work against the beholder this time only because of, dunno, a fluke of the Weave, should we house rule that it works like that, or should we stick to the game rules and, well, what was the eye beam it used on you again, Jeff?

As the DM, I think we should go with _____ YOUR OPINION HERE ______

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The mirror images can only move within your space.

As your link says.

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.

The ray is broad enough to hit an entire space, and so mirror images that hide within your space don't act like an extra skin to protect you. Baldur's Gate Mirror Images was buffed compared to the base version and was the best defensive spell in the game because of it according to some players.

You can determine which rays are broader and thinner by if they have an attack roll. If they have an attack roll, they are thin enough to be dodged.

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  • \$\begingroup\$ The issue with this reasoning is that other ray-based spell attacks would also qualify as "broad enough to hit an entire space", yet are still countered by the mirror images according to rules. So this explanation resolves this problem, but creates another. \$\endgroup\$
    – Matthieu
    Nov 9, 2022 at 10:24
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    \$\begingroup\$ If they use an attack roll, they presumably aren't broad enough, hence why they use an attack roll. \$\endgroup\$
    – Nepene Nep
    Nov 9, 2022 at 10:26
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    \$\begingroup\$ The simple rule is that if they involve an attack roll, they are not broad. \$\endgroup\$
    – Nepene Nep
    Nov 9, 2022 at 10:31
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    \$\begingroup\$ Presumably if they miss you either parry them or they don't hit your entire space. \$\endgroup\$
    – Nepene Nep
    Nov 9, 2022 at 20:10
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    \$\begingroup\$ I did give an explanation- the attack shouldn't be described as hitting the entire space if the adventurer dodges. Maybe the tarrasque sweeps their tail across the area and the player dodges down, losing an illusion to the tail for example. \$\endgroup\$
    – Nepene Nep
    Nov 10, 2022 at 1:22
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it looks like the way the spell is set up if it touches you at all it takes effect. most aimed spells, they're trying to aim for significant contact, this it seems would take effect even if it grazes.

This is backed up by the fact that it's a dex save. It's not a matter of the beholder aiming. it's a matter of can the player get out of the way fast enough.

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    \$\begingroup\$ Your supporting point isn't very solid- six out of ten of the beholder's eye rays use a save other than dex, ranging from STR to CON to WIS. \$\endgroup\$ Nov 8, 2022 at 22:37

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