If a character is grappled and stunned by a mind flayer's Tentacles attack, what can the target or another character do to end the grapple?

Question

A Mind Flayer hits its target with an attack using its tentacles. The target, a barbarian, becomes grappled, and also fails the Int save and becomes stunned:

Tentacles. Melee Weapon Attack: +7 to hit, reach 5 ft., one creature. Hit: 15 (2d10 + 4) psychic damage. If the target is Medium or smaller, it is grappled (escape DC 15) and must succeed on a DC 15 Intelligence saving throw or be stunned until this grapple ends.

Then, on its next turn, the mind flayer can use the Extract Brain action on the barbarian:

Extract Brain. Melee Weapon Attack: +7 to hit, reach 5 ft., one incapacitated humanoid grappled by the mind flayer. Hit: The target takes 55 (10d10) piercing damage. If this damage reduces the target to 0 hit points, the mind flayer kills the target by extracting and devouring its brain.

Can the barbarian do anything on his turn to break the grapple before this happens?

The stunned condition makes the creature incapacitated, which means they can't take actions (escaping a grapple is an action). Also, Stunned means they automatically fail Str/Dex saves.

Is the barbarian stuck? What kind of action could another character do to break this? I had another player character cast polymorph, but the Mind Flayer's Magic Resistance trait prevented it from working. If the MF gets another turn in combat, our Barbarian is likely dead, permanently.

I'd like to know the options my players could take, even if they don't know themselves.

Answer 1

Your players have a lot of options.

From the Grappled condition:

• The condition ends if the grappler is incapacitated (see the condition).
• The condition also ends if an effect removes the grappled creature from the reach of the grappler or grappling effect, such as when a creature is hurled away by the thunderwave spell.

So any method of inflicting the incapacitated condition on the mind flayer will end the grapple. Likewise, anything that gets the barbarian out of the mind flayer's reach will also end the grapple. There are far too many ways of achieving these to list here.

It's also worth mentioning that, since the Extract Brain ability requires the mind flayer to use an action, preventing the mind flayer from taking actions would also work. Most of the methods to do this would involve inflicting the incapacitated condition, and therefore end the grapple anyway. But as an alternative option, there's always mind control. There are a large number of spells that could be used to persuade the mind flayer not to extract the barbarian's brain, or just to let them go.

Since the mind flayer's grapple requires a Medium or smaller creature, polymorphing the barbarian into something Large should also free him. There is a minor point of ambiguity here - while the grapple can only be used on a Medium or smaller creature, it doesn't technically say anything about what happens if a grappled target becomes Large. But I think most DMs would agree that this should work.

Answer 2

The grapplee can only do something if they succeed their Int save. On a success, they would have the option to attempt to escape the grapple as an action, or do some other ability that removes them from the grapple (eg teleportation or forced movement such as misty step or thunderwave). But on a failed save, they're utterly doomed unless someone else can save them.

Polymorphing the illithid would save the grapplee, if the illithid fails its save, but with magic resistance and a good Wisdom save that's unlikely to succeed.

Essentially, you're looking to do one of the following:

• Make the illithid incapable of doing extract brain (stunned, unconscious, polymorphed, etc)
• Make the grapplee no longer a valid target to grapple (for example, by making him 2 or more size categories larger than the illithid)
• Move the grapplee and the illithid apart from each other (for example using spells such as banishment)

Answer 3

The methods that come to mind for me include:

• (a) druid cantrip Thorn Whip -- attack the barbarian (at advantage since he's stunned) and drag him away from the mind flayer.
• (b) Thunderwave, which the automatically fails the save against (again from being stunned) so it blasts him away from the bad guy. In either case, he'll take a bit of damage, but not a lot.
• Possibly a "shove" attack from anyone would work, to shove either the barbarian or the mind flayer. (If you have a Battle Master fighter, or anyone with the Charger or Shield Master feat, there are some additional possibilities there.)
• Or just a strong character who is close enough to run up, grapple the barbarian, and carry him away.

Answer 4

Simply grappling the already grappled character and then getting the barbarian out of range with half movement should suffice, likewise the same for shoving the character instead of the monster.

Nothing in RAW indicates that a grapple would be exclusive, and the forced movement you can have a grappled target do count as exactly the type of effect which ends the grappled condition.

Just going by RAW, there is not even any dice roll involved. Your target is guaranteed to fail the contest as it is incapacitated, don't try to enforce any contest with other grapplers either.

Monsters that don't intend uncontested rescue actions usually explicitly apply the Restrained instead of the Grappled condition. The main difference is that one can't be trivially ended by forced movement effects, while the other one can.

E.g. compare with the complex wording on the Gelatinous Cube, which combines Full Cover and explicit checks with Restrained to (explicitly) enforce a contest for rescue. I contrast, getting a character out of there by forced movement of any sort (despite full cover) would still not end the Restrained condition.