Advice on helping high level non-flexible casters feel useful versus magic immune creatures

[The Crimson Binome]

It is a 150ft cone. Since it can move it each round, you effectively can't move out of its range. Given the antimagic nature, the beholder doesn't just neutralise "high level non-flexible casters", it takes out everyone!

It only covers a 90-degree arc. You can get out of it by moving slightly to the side.

 

[CapnZapp]

If you're running a published adventure that has such a thing... I'd be inclined to junk that ability altogether, and give the monster some extra hit points or something to compensate. Try to estimate how much additional damage the casters in the party will deal with the restriction gone.

A level 17 party with two full casters?

As a guesstimate, I'd say +500 hit points. A caster of that level is easily capable of 100 DPR nova rounds. So five such rounds spent between two characters, taking into account three lost turns due to disabling debuffs, for a four round fight in total.

You're welcome.

 

[Quartz]

However, I'm not an experienced DM and would love to hear opinions and techniques that may have worked for you.

I haven't DMed 5e but remember the environment. The critter may be immune to magic, but the ground on which it's standing is likely not, so use Rock to Mud and then Mud to Rock to immobilise it. The critter may be immune to magic but the rock above it is likely not, so use Disintegrate to cause a rocky overhang to collapse and crush your foe. And so on.

Then there's stuff like Cloudkill. In 3E, the cloud of poisonous gas may be created by magic, but after its creation it is not itself magic. Check with your DM. Disintegrate a pit under the critter, cast Cloudkill, the gas goes into the pit, and the critter is making saves.

Then there's Gaze Reflection. Very useful for deflecting Beholder eye rays. Can it reflect a Beholder's anti-magic? Ask your DM.

Just because the critter is immune to magic doesn't mean that the critter's defensive magic can't be affected. Magic effects can be dispelled, magic items can be disintegrated or melted or shattered.

Just because a critter is immune to magic doesn't mean that it can't be entangled by a chain or net magicked by Animate Object. Telekinesis can throw things.

Are you fighting under the Leaning Tower of Pisa? Disintegrate part of the base and let the Tower collapse on your foe!

And so on.

The trick here is to give the player the opportunity to use their imagination.

 

[Gadget]

when it comes to the "endgame" fight, I don't think many people (I'm sure that there are people who do) want to just sit there as a sorcerer/bard/warlock and be like "Welp, I've got 3 spell slots that can affect Tiamat/Vecna so let me just be a haste/polymorph/shield of faith bot, run for cover, and counterspell/dispel. Much heroic, such wow, much fun."

What on earth is wrong with the above strategy? I could see if "magic immune" monsters popped up every other encounter, but even if it is the end of Campaign Encounter of all Encounters, there's nothing wrong with the spellcaster having to adjust their tactics a bit; they should have had to do this a time or two to even reach this high a level. This is especially true if, as described, it is the big climatic end campaign encounter and would have been properly foreshadowed and built up. It's not like this is a random encounter. Even a blasting Dragon Sorcerer should have picked up a modicum of flexibility along the way; a twined Haste can go a long way to help along an encounter.

That said, this is one reason why such "magic immune" creatures are vanishingly rare in published material, they do tend to shut down certain characters. This is one of the reasons why the encounter with Tiamat in the early adventures had a "stop the ritual" component and minions to not only add some spice and flavor, but give spellcasters something they could do with their spells. The above suggestions about minions and maybe a 'neutralize the enchanted ley line stones/throw the One Ring into the Fire' or some such can serve such a purpose.

 

[AmerginLiath]

Non-magic-immune minions. - Minions are a good idea anyway due to action economy.

Terrain or other features that could be manipulated using the spells that the caster has available. - I would certainly rule that magic immunity doesn't stop rocks thrown by telekinesis or falling because a supporting pillar was just blasted away.

The aforementioned buff spells.

Check on what spells the caster has available. Work out what could be done with them.

Also, foreshadow the fight a couple of levels beforehand if you can. That will allow the caster to pick and swap some spells that might be of more use.

The Cap’n had it in one. You don’t need to change any rules, just make proper preparations. That’s where battlefield control strategy in D&D came from, dealing with old-school spell-resistance in AD&D (which was crazy pants strong, especially at high levels). Change terrain to slow enemies, create walls, knock over pillars, summon creatures to fight with, telekinetically block the way in such a fashion that larger enemies are impaired (but adventurers can get back and forth) — it’s standard control wizard work, just minus the charm spells.

 

[Raif]

What on earth is wrong with the above strategy?

As I mentioned, nothing is wrong with that strategy. Some people do not enjoy that (and by that I mean for their final, built up fight having to play in the manner I outlined), and I specifically have 1 player who just won't enjoy the encounter if that's what he is "relegated" to do. As it's the final fight of the campaign, I'd rather make sure they do than go "well, them's the breaks. You're going to have to play that way for this fight". And the "Oh well just don't play with him" isn't an option, he's a long long time friend and to be frank, would rather make sure he enjoys his time.

Also, there's a difference between throwing out a twinned haste (which I agree, goes a huge way) and throwing out a twinned haste is all they can do because the encounter is immune to 70% of what this player can do.

If you took offense to that, then there was none meant. Everyone has their own playstyle and strategies should enjoy that. I know my players well enough that if I made my sorcerer player feel that way, they wouldn't get the enjoyment from that encounter beyond "Yay we finished the campaign". On the other hand, I have a player who plays clerics and such in that exact way and she loves it. Different strokes for different folks.

The Cap’n had it in one. You don’t need to change any rules, just make proper preparations. That’s where battlefield control strategy in D&D came from, dealing with old-school spell-resistance in AD&D (which was crazy pants strong, especially at high levels). Change terrain to slow enemies, create walls, knock over pillars, summon creatures to fight with, telekinetically block the way in such a fashion that larger enemies are impaired (but adventurers can get back and forth) — it’s standard control wizard work, just minus the charm spells.

For a wizard, swapping spells is easy. The problem I had in mind was more for a sorcerer who can't do so without proper warning. Cap'n did get it in one to foreshadow the fight giving them time to swap a few spells at least and adding in minions and stuff like you mentioned will give them things to do.

 

[Ancalagon]

It is a 150ft cone. Since it can move it each round, you effectively can't move out of its range. Given the antimagic nature, the beholder doesn't just neutralise "high level non-flexible casters", it takes out everyone!

Beholders are scary in a way demons and dragons will never be. Which is as it should be.

... but doesn't the antimagic cone also neutralize its own powers? Stay in the cone, riddle it with arrows no?

 

[Quartz]

Zap it from behind with Blindness.