D&D 5E Elder Brain Armor--Volo's Guide gap

According to the Mind Flayer subsection of the Monster Lore Section of Volo's Guide to Monster (VGM), "ELDER BRAIN RESTING POOL. Usually centrally located, the lair's resting pool is where the elder brain holds court in its brine pool, protected by a nearly impenetrable layer of a glass-like substance that blocks all attacks except for psionic abilitie" (VGM 78, emphasis mine).

In the bestiary section, however, the Elder Brain stats give the Armor Class as "10" and make no mention of the impenetrable glass-like protective enclosure.

I've seen other stat blocks for the elder brain created by fans before VGM that give the AC as 21. I'm wondering if there is precedent from earlier editions for AC with the protective enclosure.

My game doesn't use the UA Mystic class and none in the party have psionic attacks. So how would they damage the elder brain?

My thought is that while their attacks can't penetrate the enclosure, they may bash it hard enough to cause the EB to smash against the side and take damage--elder concussion

Also, I would give HP to the enclosure. It may block all attacks from hitting the EB, but eventually it will crack and break open.

Also, on the map in VGM they have an ELDER BRAIN CHAMBER and a RESTING POOL. The room descriptions, however, list only an "ELDER BRAIN RESTING POOL" which seems to conflate the too. I'm thinking that maybe the EB goes to the chamber, within the protective enclosure to "hold court" and to take a defensive position if their is a breach, but that it needs/desires to "stretch out" and rejuvinate in the resting pool. So there may be a small chance of encountering it with the lower hp if the party is somehow able to sneak up on it.

I'm interested in knowing if there are older material that give some precedent for how to stat up an EB in its protective enclosure.

The AC inside the enclosure is ∞ except against psionic attacks.

The AC outside of the enclosure is 10.

Edit: Made a correction.

Also, consider there are ways to draw it out of the enclosure and ways to attack it without dealing with AC. It's a boss fight; encourage the players to get creative.

I would not interpret it as saying the enclosure is itself invulnerable. Just that you cannot attack the EB through the enclosure. So decide on how much damage must be dealt to the enclosure in order to break it.

Volo encountered on that had cast a Wall of Force.

Flamestrike said:

Volo encountered on that had cast a Wall of Force.

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I like this, but... a Wall of Force is a Concentration spell and would not fully enclose the EB. Also, the spell description says nothing about psi damage getting through. Actually a wall of force is immune to psi damage as well (immune to ALL damage).

When you think about it, the EB in the glass-like enclosure WITH wall of force up is damn well defended. At it should be.

So, no, the glass-like enclosure is separate from its wall-of-force lair power.

jaelis said:

I would not interpret it as saying the enclosure is itself invulnerable. Just that you cannot attack the EB through the enclosure. So decide on how much damage must be dealt to the enclosure in order to break it.

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Exactly, but I was hoping that their might be some precedent that could give me a reasonable number of HP the enclosure will have.

Ah, yes, that makes sense. It isn't hard to hit the enclosure. So, again, I'm just left with coming up with HP.

I can't see any reason an EB would leave its protective enclosure when it knows their is even a potential threat to it. All of its psi attacks work from within it.

ArchfiendBobbie said:

The AC inside the enclosure is ∞ except against psionic attacks.

The AC outside of the enclosure is 10.

Edit: Made a correction.

Also, consider there are ways to draw it out of the enclosure and ways to attack it without dealing with AC. It's a boss fight; encourage the players to get creative.

Click to expand...

The Elder brain may not want to leave the enclosure, but there has to be a way into it. If for no other reason than to get tadpoles into the pool.

MNblockhead said:

Ah, yes, that makes sense. It isn't hard to hit the enclosure. So, again, I'm just left with coming up with HP.

I can't see any reason an EB would leave its protective enclosure when it knows their is even a potential threat to it. All of its psi attacks work from within it.

Click to expand...

What Leatherhead said. Let them find a way in and then see what they do to drag it out. Or if they find some advantage you're not considered (like using magic to try to boil it alive).

If you look at the picture on VGM 73, you see two Quaggoths chained to and pulling a levitating elder brain in a glass-like enclosure.

In the description for the "Tadpole Chambers" on VGM 78, it stats "The elder brain dictates that populations of tadpoles be kept in smaller pools under guard, away from the brine pool. Should the brine pool be destroyed in an attack, these tadpoles stand a better chance of survival."

On the map on page 79 there are two tadpole chambers off to the side of the "Resting Pool." Also, the Elder Brain Chamber is above the Resting Pool and seems to show an Elder Brain in an enclosure similar to that depicted on page 73 but which is set into the ground or a low dias. I'm assuming that the enclosure is filled with brine.

There seems to be an opening that implies that perhaps the elder brain can levitate down from its enclosure into the resting pool below. That could be one weakness. If the party can manage to attack from below. The EB will still have the Wall of Force lair action, but it allows for an opening of the party getting in some big hits.

Also, given the damage an EB can give out, along with its mind flayer, grimlock and quaggoth minions, I don't think that the enclosure has to be that tough. Yes, it block ALL damage to the EB until it is destroyed, BUT it needn't have very high HP. Perhaps 25% of the EB's HP, so 30-75, or 53 if you go with the default of 210 HP for the EB.

I will likely also rule that barrier can only take damage from bludgeoning and piercing damage. None from slashing, fire, acid, etc.

Once the enclosure is destroyed the EB would levitate down into the resting pool, casting a wall of force on the portal separating the EB Chambers from the Resting pool. This would be not only to get away from the players, but also because it needs to be in the brine solution to survive. They could get one opportunity attack and then would need to find their way down to the resting pool.