D&D 5E Am I reading the Mind Flayer attack right?

[iserith]

I plan on throwing a couple of them at the party next week, but the warlock has Repelling Blast, so any theoretical grapple is unlikely to last more than a round.

Dangling from the ceiling of the mind flayers' lair are the pale roots of Dzéwà, The White God, which tap into this world from the Far Realm. Tipped with lamprey-like mouths, the roots hunger for eldritch energy and viciously attack any who summon it (as a reaction, piercing and acid damage plus ongoing blood drain). A warlock whose patron is the Great Old One can make himself or herself immune to this danger in exchange for a modicum of sanity. All others must refrain from calling upon their eldritch power or pay with blood.

 

[The Crimson Binome]

Have the mind flayers grapple the warlock then

If the second one witnesses the first one being blown away by the warlock, then that will definitely be its next course of action. It's also possible that the whole party will be stun-locked from the first mind blast, if they keep failing their saves. It could go either way.

 

[Endur]

I plan on throwing a couple of them at the party next week, but the warlock has Repelling Blast, so any theoretical grapple is unlikely to last more than a round.

Does repelling blast end grapples?

 

[The Crimson Binome]

Does repelling blast end grapples?

Any forced movement ends a grapple automatically. You could blast away the mind flayer, leaving the PC in place, or you could blast away the PC (I guess if you had trouble hitting the mind flayer, for some reason).

 

[spectacle]

Any forced movement ends a grapple automatically. You could blast away the mind flayer, leaving the PC in place, or you could blast away the PC (I guess if you had trouble hitting the mind flayer, for some reason).

More specifically, forced movement that results in the grapplee being out of reach of the grappler will end the grapple. Most creatures have 5 or 10 foot reach so it's usually not hard, but there are some creatures like the Roper that have extremely long reach.

 

[Imaculata]

Dangling from the ceiling of the mind flayers' lair are the pale roots of Dzéwà, The White God, which tap into this world from the Far Realm. Tipped with lamprey-like mouths, the roots hunger for eldritch energy and viciously attack any who summon it (as a reaction, piercing and acid damage plus ongoing blood drain). A warlock whose patron is the Great Old One can make himself or herself immune to this danger in exchange for a modicum of sanity. All others must refrain from calling upon their eldritch power or pay with blood.

Basically you could add any number of details to the encounter that make the use of Eldritch magic, or the act of moving the Mindflayers a bad idea. Some more ideas:

-The Mindflayers have powerful guardians in stasis pods, which awaken when Eldritch magic is used near them, or when the pods are directly attacked.

-Healing pools litter the area, which heal the Mindflayers with evil energy if they are pushed into them.

-Pillars limit line of sight, and block the beams of Eldritch Blast, plus they also limit how far back the Mindflayers can be pushed.

-An ambient magical effect makes push and pull spells ineffective. The Mindflayers are nailed to the floor.

 

[MarkB]

Basically you could add any number of details to the encounter that make the use of Eldritch magic, or the act of moving the Mindflayers a bad idea. Some more ideas:

-The Mindflayers have powerful guardians in stasis pods, which awaken when Eldritch magic is used near them, or when the pods are directly attacked.

-Healing pools litter the area, which heal the Mindflayers with evil energy if they are pushed into them.

-Pillars limit line of sight, and block the beams of Eldritch Blast, plus they also limit how far back the Mindflayers can be pushed.

-An ambient magical effect makes push and pull spells ineffective. The Mindflayers are nailed to the floor.

Or, y'know, not do that, and let the warlock's player feel good about having a useful ability for the encounter rather than nerfing it in advance.

 

[iserith]

Basically you could add any number of details to the encounter that make the use of Eldritch magic, or the act of moving the Mindflayers a bad idea.

I prefer to think of it as a trade-off or a challenge to overcome before being able to push the mind flayers around.

The difficulty of the encounter should be stepped up on one in this case.

 

[Endur]

More specifically, forced movement that results in the grapplee being out of reach of the grappler will end the grapple. Most creatures have 5 or 10 foot reach so it's usually not hard, but there are some creatures like the Roper that have extremely long reach.

Is this actually in the rules somewhere or is this an interpretation? If we're just interpreting, we could just as easily rule:
1) grapple ends due to forced movement;
2) No forced movement (not being repelled) due to grapple; or
3) both grappling parties get repelled some amount of distance.

(or if you want to be real cruel, 4) repelling blast causes mind flayer and the ally's brain to travel 10' away from the ally's body)

 

[The Crimson Binome]

Is this actually in the rules somewhere or is this an interpretation?

It's actually in the rules, with very little room for interpretation. I'll quote the Basic Rules document, for the GRAPPLED 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 thunder.wave spell.