D&D 5E Forcecage and Beholders

[Staffan]

Blindness absolutely stops all eye rays (except the central eye).

I was thinking that that doesn't seem right, but I went to actually look at the description and you're right.
Eye Rays. The beholder shoots three of the following magical eye rays at random (reroll duplicates), choosing one to three targets it can see within 120 feet of it:

Blind beholder can't see anything, so the eye rays turn off.

As for the Forcecage, I believe the correct ruling would be that there is no rule basis under either the Disintegration effect of the Beholder or the Forcecage spell that would make it vulnerable to disintegration.

Disintegrate says "This spell automatically disintegrates a Large or smaller nonmagical object or a creation of magical force. If the target is a Huge or larger object or creation of force, this spell disintegrates a 10-foot- cube portion of it." There's nothing about the forcecage spell that says it shouldn't work.

With regards to what happens when the Beholder approaches the Forcecage wall with the central eye open and starts to try to pass through: This is not a situation covered by the rules. The 'partially within the spell' language applies only when the spell is cast. Accordingly, the adjudication of this interaction is up to the DM.

I disagree. A beholder's anti-magic ray works like an antimagic field, except cone-shaped. These would be the relevant parts of the description:
Spells and other magical effects, except those created by an artifact or a deity, are suppressed in the sphere and can't protrude into it.
[...]
Areas of Magic. The area of another spell or magical effect, such as fireball, can't extend into the sphere. If the sphere overlaps an area of magic, the part of the area that is covered by the sphere is suppressed. For example, the flames created by a wall of fire are suppressed within the sphere, creating a gap in the wall if the overlap is large enough.

The situation with forcecage is exactly the same as with wall of fire. The anti-magic cone creates a hole in the spell, but due to geometry the hole is not large enough for the beholder to leave.

 

[Paul Farquhar]

This issue arose in game a couple of weeks ago. The PC was trapped in a force cage, but did not realise they could use Disintegrate to escape, because unlike Wall of Force the Force Cage spell does not mention Disintegrate. However, the relevant text is in the Disintegrate spell text.

Now, a DM could rule that the Beholder's disintegrate ray does not function the same as the spell. But when it comes down to DM's call, escaping is likely to be the most entertaining outcome. The player should have chosen a better spell to cast.

 

[Sorcerers Apprentice]

Now, a DM could rule that the Beholder's disintegrate ray does not function the same as the spell. But when it comes down to DM's call, escaping is likely to be the most entertaining outcome. The player should have chosen a better spell to cast.

The rule about the beholder's disintegration ray destroying "creations of magical force" is right there in the monster description, so there's actually no need to reference the Disintegration spell in this situation.

The DM can of course rule however he wants. But when the rules text is this explicit, saying that Forcecage is immune to beholder disintegration would IMO be a house rule rather than a ruling.

 

[Staffan]

Ironically, I would probably rule that a beholder caught in a forcecage and with its central eye open, who used its disintegrate eye beam to destroy the cage (or part of it) would leave the part caught in the antimagic cone intact, once the central eye is closed or looks elsewhere. So there'd be a small circle of force bars hanging in the air.

 

[jgsugden]

...
Disintegrate says "This spell automatically disintegrates a Large or smaller nonmagical object or a creation of magical force. If the target is a Huge or larger object or creation of force, this spell disintegrates a 10-foot- cube portion of it." There's nothing about the forcecage spell that says it shouldn't work.

The eye beam is not the spell. It does not say, "as the spell" or reference the mechanics of the spell (as we see for the antimagic cone/antimagic field). In the same way that different fire spells and effects operate differently (some impact objects some do not, some light things on fire, others do not), disintegration does not inherently work the same way when originating from different sources.

I disagree. A beholder's anti-magic ray works like an antimagic field, except cone-shaped. These would be the relevant parts of the description:
Spells and other magical effects, except those created by an artifact or a deity, are suppressed in the sphere and can't protrude into it.
[...]
Areas of Magic. The area of another spell or magical effect, such as fireball, can't extend into the sphere. If the sphere overlaps an area of magic, the part of the area that is covered by the sphere is suppressed. For example, the flames created by a wall of fire are suppressed within the sphere, creating a gap in the wall if the overlap is large enough.

The situation with forcecage is exactly the same as with wall of fire. The anti-magic cone creates a hole in the spell, but due to geometry the hole is not large enough for the beholder to leave.

As the beholder approaches, the hole shrinks. However, it is up to the DM if it shrinks to zero before it hits the eye of the beholder. The rules are not that specific. If the beholder's eye is within the wall space, it is a situation that is not covered by the rules of Forcecage.

Regardless, it should be up to the DM, whether it is RAW or a deviation from the rules, and the player should accept the ruling. So, to that extent, it is irrelevant whether we agree on the RAW.

 

[Lyxen]

The eye beam is not the spell. It does not say, "as the spell" or reference the mechanics of the spell (as we see for the antimagic cone/antimagic field). In the same way that different fire spells and effects operate differently (some impact objects some do not, some light things on fire, others do not), disintegration does not inherently work the same way when originating from different sources.

When specifically specified as different, I agree they would not behave in the same manner, but otherwise, Occam's razor would say that it's intended to behave the same way. In any case, it's irrelevant since, on the subject of magical force, both are specified to work the same way:

• Spell: This spell automatically disintegrates a Large or smaller nonmagical object or a creation of magical force. If the target is a Huge or larger object or creation of force, this spell disintegrates a 10-foot- cube portion of it.
• Monster: If the target is a Large or smaller nonmagical object or creation of magical force, it is disintegrated without a saving throw. If the target is a Huge or larger object or creation of magical force, this ray disintegrates a 10-foot cube of it.

As the beholder approaches, the hole shrinks. However, it is up to the DM if it shrinks to zero before it hits the eye of the beholder. The rules are not that specific.

Actually, even if the hole is the size of the eye of the beholder, it would still not allow passage anyway, I don't think beholder are like octopi.