Does Fog Cloud render a Beholder's eyestalks ineffective?

Question

The fog cloud spell creates "heavily obscured" vision, which effectively acts like the blinded condition for characters in it, per the answer to this Q&A: Interaction between fog cloud and new vision errata rule

A beholder's eye stalks (Monster Manual, p. 28) can target "one to three targets it can see within 120 feet of it." Thus like many spells, this seems to suggest it must see its target.

The central eye of the Beholder has an Antimagic Cone (essentially an antimagic field) in a 150 foot cone. Antimagic Fields simply temporarily suppress magical effects into which they come in contact. As the central eye turns away, the Antimagic Cone will sweep away in another direction and the fog cloud returns, as suggested by the answer to this question: What happens to area-effect spells like Darkness or Fog Cloud when an Antimagic Field moves?

If, however, the Beholder tries to use its eyestalk's spell effects to target something it can see in the cone, the Antimagic Cone prevents the magic from working.

Lastly, the Beholder has no dispel magic spells for the fog cloud.

In effect, with fog cloud, the Beholder either cannot see the characters to target them or when it can see the characters its eye stalk spells do not function.

Are we interpreting this correctly or is there some other way for the Beholder to use its spells in a fog cloud?

Answer 1

Excellent Idea! (MAYBE there's a loophole)

First of all, I'm impressed by this strategy! It's a great idea, and turns the tables on the Beholder extremely well. You might have some trouble targeting the Beholder from within the cloud yourself, but characters normally know where other creatures are during combat (the fact that the Beholder hovers may complicate this, but probably not unless the Beholder takes the Hide action).

There is a small potential loophole I noticed, but it's not ironclad (more open to interpretation).

Legendary Action & Lair Actions

The Beholder can use its eye rays with its Action during its turn, but must choose targets it can see. However, it can also use its eye rays in two other ways: one is with a Legendary action at the end of another creature's turn. This legendary action is described as follows:

Eye Ray. The beholder uses one random eye ray.

It can also use lair actions, one of which is the following (MM, p. 27, bold added):

Walls within 120 feet of the beholder sprout grasping appendages until initiative count 20 on the round after next. Each creature of the beholder's choice that starts its turn within 10 feet of such a wall must succeed on a DC 15 Dexterity saving throw or be grappled.

Note that neither of these descriptions requires the Beholder to see its chosen targets.

It's likely that the definition of the eye rays given in the Actions section of its description is meant to apply to the other (Legendary) rays as well. But this is ambiguously worded, and open to interpretation. Clearly, some parts of the description of the eye rays must apply (or else there would be no limit to the range of these Eye Rays, for example): exactly how much applies, though, is ultimately up to the DM.

Even if its lair and Legendary actions do not require sight, note that your strategy would pretty much halve the amount of opportunities that the Beholder has to target creatures directly (as opposed to lifting a heavy object above a character while they are in the Antimagic Cone, and dropping it). This makes this strategy an excellent idea in any case.

Answer 2

You are correct.

After some research and deliberation, it seems your method is legit and the easiest way to deal with a beholder in an enclosed space if your party can deal with it in an Antimagic Cone/Fog Cloud area.

Since RAW the Beholder must see its targets (Is it intended? Maybe we'll never know.), it can't blindly shoot the area. Deal with the bite attack and you're done.

Answer 3

A Great use of Cover

A masterful interpretation of the rules. The eyes require targeting and the main anti-magic eye can only suppress magical effects, it will not dispel them. If a player finds themselves in a fog cloud or the anti-magic field they cannot be targeted or harmed by the eye stalk beams. This would work with any spell based vision blocking effect for example darkness.

The Beholder is not completely without options however. It can hold its action to release all of its eye beams when it sees a valid target. Much like any other creature it is allowed to hold its action for a time where it feels there is better opportunity. If someone were to step out of the cloud, to attack, they might find themselves the target of 3 beams at once.

The Beholder could also disintegrate segments of the terrain, like walls, floors or ceilings to have them collapse around or on top of the party. Technically it could also use its telekinesis to throw boulders into the cloud.