D&D 5E Elder Brain Sense Thought vs Warlock Thought Shield

[beaumontsebos]

Would an Elder Brain using Sense Thoughts still be able to use the part of the feature to deceive a creature's mind on a Warlock with Thought Shield? Assume the Psychic Link with the Warlock has been established.

Relevant texts:

Elder Brain Sense Thoughts: The elder brain targets a creature with which it has a psychic link. The elder brain gains insight into the target's reasoning, its emotional state, and thoughts that loom large in its mind (including things the target worries about, loves, or hates}. The elder brain can also make a Charisma (Deception} check with advantage to deceive the target's mind into thinking it believes one idea or feels a particular emotion. The target contests this attempt with a Wisdom (Insight} check. If the elder brain succeeds, the mind believes the deception for 1 hour or until evidence of the lie is presented to the target.

Warlock Thought Shield: Starting at 10th level, your thoughts can’t be read by Telepathy or other means unless you allow it. You also have Resistance to psychic damage, and whenever a creature deals psychic damage to you, that creature takes the same amount of damage that you do.

My Initial Take: Thought Shield would for sure prevent the first part of the Sense Thoughts feature. However, the second part of the feature doesn't really require the Elder Brain to read the Warlock's thoughts. So, it would be able to use the part of the feature on the said Warlock.

What say you?

 

[Dausuul]

Rules as written: I agree, you are correct.

How I would rule it at the table: The brain can use the second half of its ability, but it loses the advantage it would normally have on the check, because it can't tailor its deception to the warlock's thoughts; it is "shooting blind."

 

[JiffyPopTart]

I'd say Though Shield is so rarely used that you should throw the character a bone and let them be immune to it (which probably would make the Elder Brain very curious if not angry at the warlock).

 

[Fenris-77]

Yeah, I'd give the Warlock a pass here. This kind of shizz is exactly where thought shield is supposed to shine. I'm not going to RAW that up.

 

[beaumontsebos]

Thanks all.

I tend to agree with the general consensus here. The Elder Brain did establish the Psychic Link with the Warlock, so the Warlock is aware something is in his brain. And now the Elder Brain knows that the brain it has infiltrated has resistances against it. Makes for an interesting internal side story.

 

[3catcircus]

I think the key is parsing the first and second sentences of the description of elser brain sense thoughts. The elder brain gains insight into. Not, reads thoughts, gains insight into. So - it gets a general idea of how the creature thinks, its current emotional state, and its surface thoughts (thoughts that loom large - i.e. current worries and concerns, driving the current emotional state). Warlock Thought Shield concentrates on the reading of thoughts (through primarily Telepathy) - the 8th level spell Telepathy describes it as occurring with a willing creature with which the caster is familiar and that you can share words, images, sounds and other sensory messages. Same requirement for telepathic bond to be a willing participant. I don't see how the description of warlock thought shield stating "unless you allow it" is any different than the requirement for telepathy or telepathic bond to require willing participants - so it doesn't really buy you any additional benefit in that regard. It would, I think, protect against use of the Detect Thoughts spell, beyond the detection of surface thoughts since a deeper probing is what requires a Wisdom check - use of Detect Thoughts ought to be allowed only to read surface thoughts, but the attempt to probe deeper should be what is protected against by warlock thought shield.

I would rule that Warlock Thought Shield does not protect against Elder Brain Sense Thoughts, but would result in no advantage on the opposed check since implanting a false memory, emotion, etc. is equivalent to a deeper probing.