How can a BBEG deal with a Wall of Force and Sickening Radiance spell combo without trivializing it?

Question

This question has already been asked in general form here, but was closed as too broad: "How to deal with broken combos?". I'm going to make an effort to make the scenario I'm asking about more specific to keep my question open.

The spell sickening radiance (XGtE, p. 164), cast just before a wall of force (through a readied action or something similar) can trap and kill many solo Big Bad Evil Guys (BBEGs), with just two casters. This combo is particularly lethal because of the levels of exhaustion the spell gives, but could work even with other persistent damage spells. Sickening radiance is a spell that creates a persistent area of effect for 10 minutes that deals radiant damage and gives exhaustion on failed saves.

The combo works like this: wall of force (WoF) caster readies their action, with the trigger "cast WoF on the BBEG when my friend casts sickening radiance (SR)". SR caster's turn comes, and they cast SR, centered on the BBEG. WoF gets cast on the BBEG as a sphere, trapping the BBEG within the wall of force for 10 minutes while they get exhausted to death.

What actions can I, as a DM, take to make a fight with a BBEG not as trivial, while still rewarding the two spellcasters' ingenuity?

I classify "rewarding the two spellcasters' ingenuity" as at least forcing the BBEG to spend a limited resource to deal with the problem. So a BBEG having disintegrate is one option for what I can do, but giving the BBEG a teleport as an action (or legendary action) is not.

Answer 1

Fight magic with magic

There are many spells available to spellcasters to either stop or suppress the spells in this combo. These options require the BBEG to use up spell slots (potentially high level spell slots), and many of them will require the BBEG to be exposed to the combo for at least one round.

If the BBEG is not a spellcaster and does not have magic items which can cast some of these spells on their behalf, their options are sorely limited.

Counterspell

If the players are within 60 feet of the BBEG when they enact this plan, the BBEG will want to cast counterspell. Since the player characters are readying an action to cast a spell, it should be obvious to any BBEG worth their salt that they are about to enact some nasty combo and that they should stop that.

However, the BBEG only gets one reaction, so they can only counter one spell. There is the choice of countering wall of force or sickening radiance. They can only stop one spell. If the party did not coordinate their actions, they may have allowed the BBEG a turn between the two casters such that the BBEG could counter both spells. Thus counterspell rewards the players for good teamwork while preventing them from trivialising the encounter.

Note that if Readying a spell is involved, counterspell must be used when the spell is Readied, because that is when casting takes place.

Dispel Magic

If the BBEG is hit by this combo, they can cast dispel magic on sickening radiance. They are still stuck inside a wall of force, which is not a good place to be, and they may have taken damage from one round of sickening radiance if they failed their Constitution save. The BBEG's escape will be sufficiently delayed that the party might gather into a more advantageous position.

Disintegrate

If the BBEG is high enough level to have disintegrate, then they can use it to get rid of the wall of force. They can then walk out of the sickening radiance, although they'll still have faced at least one round of sickening radiance (depending on their speed). Forcing the BBEG to use their disintegrate on a wall of force and not a player character is a substantial advantage.

Antimagic Field

The nuclear option for high-level spellcasters fighting against other spellcasters. This will allow the BBEG to completely ignore both sickening radiance and wall of force. However, it also suppresses any buff spells the BBEG may have had active and prevents them from casting other spells, although they can always drop concentration on antimagic field once they are clear of the combo. This costs an eight level spell slot, though, so is a very costly counter to the combo.

Globe of Invulnerability

This spell has a similar effect to antimagic field, in that it completely negates wall of force and sickening radiance, but it uses a lower level spell slot (although at 6th level its still significant) and doesn't stop the BBEG from casting spells. But the casters can also keep casting spells at the BBEG by moving to within 10 feet of the BBEG.

Etherealness

Wall of force prevents escape via the Ethereal Plane, but side-stepping to the Ethereal Plane allows the BBEG to ignore sickening radiance. Etherealness's 8 hour duration allows the BBEG to wait out the spells of the combo and then move into a more advantageous position (or possibly flee). This requires the BBEG to spend a 7th level spell slot.

Harm the casters, break their concentration

The BBEG might have some way to harm the characters without attacking them directly. BBEGs regularly have minions (and if your BBEG doesn't have minions, why not?). The BBEG would order their minions to focus fire on the two casters, attempting to break their concentration.

However, you specify solo BBEG. If adding minions is not an option, you can instead consider adding lair actions. Lair actions will function as long as the BBEG is alive and can be used to affect the party even if the BBEG can't reach them personally.

Until such time that concentration is broken, though, the BBEG is trapped, unable to fight directly, and making saves against sickening radiance. Depending on circumstances, it might be many rounds before the BBEG can escape. This rewards the party's ingenuity.

Teleport out of there

Wall of force does not block teleportation (unlike its higher level counterpart forcecage). If the BBEG has spells such as dimension door or misty step, they can escape the wall of force and continue the fight. (Note that misty step has a range of Self, meaning it is unaffected by wall of force providing total cover.) Misty step is a rather cheap counter, being only a second level spell and a bonus action, but it is also a commonly available one. Dimension door, being only a fourth level slot, also causes the players to have spent more resources than the BBEG, but it is also something which a moderately levelled spellcaster is likely to have.

Spells such as teleport or plane shift can be used by the BBEG to escape the battle entirely. If the goal of the players was to kill the BBEG this is no good for them, but otherwise this leaves the BBEG's lair undefended for the players to loot or demolish or whatever.

Answer 2

The bad guy could wall off the effect.

While the sickening radiance spell can go around corners, a spell that can provide total cover across the entire width of the sphere could wall off the effect. Possible spells for this include wall of stone, wall of ice, or of course another wall of force.

Some spells would allow him to take cover using the existing environment, for example meld into stone would allow the guy to hide underground or in a wall for the duration (assuming the floor or wall is partially or wholly stone). He could potentially escape entirely by going under the edge of the wall of force, but waiting out the sickening radiance will allow him to get rid of the exhaustion levels it caused. Similarly any effect that would grant access to the Ethereal plane would allow him to hide out there until the spells expire, even if the wall of force keeps him in the bubble for the duration.

Any spell that specifically blocks spell effects would also protect him. Otiluke's resilient sphere would block the effect, for example, but only for 1 minute. It might give the target enough time to figure out his next move, though, or time for his minions to deal damage to the casters and break their concentration.

Answer 3

Use minions (and maybe spells) to break the spellcasters’ concentration

Both sickening radiance and wall of force require concentration, and any big bad evil guy (BBEG) villain NPC who has higher level spells like disintegrate at their command will surely understand how to spot that, even if they they’re not familiar with the spell. So they could direct their minions - which hopefully they have - to focus their attacks on the spellcasters. If either fails a concentration check, the combo is broken without the BBEG having to do anything themselves.

This approach rewards the players’ through opportunity cost, and also enables the other player characters to aid the plan by trying to protect the spellcasters until the BBEG is defeated.

If the BBEG is going solo, and depending on your interpretation of what spells are blocked by wall of force, they might be able to cast their own spells to damage the spellcasters and hopefully break their concentration. This might be a surer tactic since even though minions might provoke more checks through multiple attacks, a good mid-level spell could potentially do a great deal more damage, making a save much harder to pass. And they only have to break the concentration of one of the PCs to break the combo; probably sickening radiance is a better bet.

Note too that even if they cannot break the concentration on either spell from behind the wall of force, they have an earlier opportunity. Readying the wall of force spell requires holding on to the cast spell as though concentrating until the trigger for the readied action. So if the villain recognises the PC is going to cast a major spell, they can cast a damaging spell or another attack on them to cause them to lose the wall of force before it’s cast - assuming they get a turn in between.

Let the attack affect the BBEG’s tactics

Another option is for the BBEG to deal with it themselves, but let this affect their judgment - perhaps they are outraged at having been trapped like that, or if they are successfully made exhausted, they grow desperate to end the fight. So even though the tactic has failed to defeat the BBEG, it has made the fight easier because the BBEG is making mistakes or taking riskier actions. This is easily combined with the above: if it takes more than a turn or two of attacks to break the spellcasters’ concentration, the BBEG can make a short villain speech about having to do everything themselves before using distintegrate or another limited magical resources to escape.

Answer 4

Combat Doesn't Happen in a Vacuum

There are a lot of things that need to go right for this spell combo to work.

• They both have to have a higher initiative than BBEG with that trigger. If they beat either caster, and can close distance, it can complicate things quite a bit. I know you can say, they can get off a round of whatever and likely not take out one of the casters, but
• The BBEG needs to be vulnerable to exhaustion effects (Not undead, a construct, etc.)
• The BBEG can't have any restorative items/magic/Hero Points (Re: Ways to Remove Exhaustion)
• If they can cast Sickening Radiance in, BBEG can cast other spells out
• Requires BBEG to be alone, or that all allies are adjacent
• Requires BBEG to have no travel magic or sheltering spells
• Requires the fight to be taking place in a completely calm environment and not challenging the concentration on its own
• Which also includes, if they're in the BBEG's lair, there could be traps.
• BBEG, even at the most stripped down can arguably break concentration with solid social rolls, IE the Poisonous Captive
• They may need the BBEG alive to disarm the doomsday weapon or know the location of the McGuffin

Answer 5

A few more approaches (since it seems likely you will need to address this many times in your campaign):

I am one with the elements

@CatLord's bucket list covers this (immunity to exhaustion), but turning into an elemental [1] is a relatively painless way to avoid the exhaustion portion of it. You may still need to deal with the significant radiant damage somehow.

... and your little dog too

Drop a captive or innocent in the same square as BBEG, no AOE to start off fights.

The two can be separated by choosing what side of the barrier the two end up on, as long as the victim can survive the first round of Sickening Radiance (@RedOrca)

Death is not an option

Being possessed, dominated, confused or misled might mean that the bubble of death is inappropriate.

A case of mistaken identity

Clone, illusion, doppelgängers, etc. can feel cheap (recently my party unloaded 10 minutes of planning to explode a Gas Spore decoy), but it mixes things up.

I'm not trapped in here, you're trapped out there

If the caster is next to the doomsday device, the rest of the room is filled with lava, the party might prefer to be inside than outside several minutes waiting for failed Con saves.

Dig dig dig

Wall Sphere of Force doesn't extend past total cover. You can just dig underneath it - either with your monstrous strength, a variety of spells, and even cantrips [2].

This will not work against suspended-in-air spheres or boxes. (@Marq)

Kobayashi Maru

When there is no way to win... Feign death, greater invisibility (prevented by sickening @CatLord), major image yourself teleporting - hope they don't sit around concentrating for the 5 remaining minutes before you would die.

• [1] What happens when exhaustion passes 6th level on an immune creature?
• [2] https://www.dndbeyond.com/spells/mold-earth

Answer 6

As a DM, I feel the whole point is to get a great story and cap it with something epic that everyone wants to talk about again and again. I have had pretty good luck with creative results that just bend the expectations a bit. With that in mind...

It looks like the players may be making certain assumptions about their spells that a tricky DM should be able to bend to their will. Wall of Force states,

An invisible wall of force springs into existence at a point you choose within range.

It says nothing about being immobile. Sphere's roll. Time to crush some players with a lovely unbreakable wall or if you want to be nice about it, just roll out of the Sickening Radiance spell, smile and wait.

You could also, burn a reaction, cast Enlarge on yourself and get pushed to one side of the sphere as you are now too big to fit inside of it. If you really want to have a story, have the BBEG die in front of them and slowly convert to a Revenant over 10 minutes, then give them another fight. I think it would be safe to grant the Revenant Immunity to the damage and conditions that ended its life so they don't try it again.

Answer 7

Lets establish first that since Wall of Force is a 5th level wizard-only spell then the Wizard who casts it would have to be a 9th level wizard*. So the BBEG would have to be a CR9 or higher creature.

The solution is to use extra enemies exploit how you have two casters in the party who cannot use any other concentration spells and both must maintain their concentration. Have allies of the BBEG emerge to attack the party, specifically to break the concentration of the spellcasters. The issue is what enemies can survive very long, I will explain how there's many options there.

Quite a few things have to NOT be the case for this combo to kill the BBEG before their concentration is broken:

1. the target has to not have a good save against Sickening Radiance
2. the target has to not be immune to the exhausted condition
3. the target has to not have any magic that neutralizes the Sickening Radiance
4. the target must not have any means of teleportation or other equivalent travel

If they have high constitution save it will take too long for them to fail 6 constitution saves even considering that after failing 3 times they will have disadvantage on constitution saves. For example a Cloud Giant has a +7 on constitution saves so only a 9% chance they'll fail the first 3 saves. Also all creatures with decent constitutions saves but magical resistance will take too long to be eliminated.

Constructs and undead are generally immune to the exhausted condition, not just those it's common on many creatures in the Monster Manual, only dealing 4d6 damage per round isn't what makes this combo special. Just pick any of the creatures with immunity to the exhausted condition and this combo will be too slow.

While Wall of Force is very hard to negate, there's many options to negate the Sickening Radiance such as Dispel magic or any spell that blocks its line of effect.

So lets try to apply the following criteria to all the creatures in the Monster Manual:

• Medium/low constitution save
• No magic resistance
• No immunity to the exhausted condition
• Cannot cast Dispel Magic
• Cannot teleport nor other magical travel (like Plane Shift)
• Is Challenge Rating 9 or higher.

Not a single creature in the Monster Manual fit all those criteria.

There are additional problems even if you go outside the Monster Manual.

Both casters must win on initiative as whichever caster goes first and holds a spell it will be obvious they are casting a spell and cannot depend on reactions to use defensive spells like Shield. Or if an enemy spellcaster they can cast Counterspell.

If you add the further requirement of them having low dexterity (Dex Score 11 or lower) then there's almost nothing left even from sources outside the Monster Manual.

A DM can deliberately exploit these and make the challenge of the fight being simply to maintain concentration on both spells as there's an onslaught of attacks and the two casters are unable to use concentration spells to help the attacks.

A DM never has to show his or her cards, they can pull out "and here are the BBEG's bodyguards who have been waiting to be called into action" but you only decided such other enemies should exist because of this combo being used.

*A Wizard below 9th level could cast a 5th level scroll but it would not be practical as under the Scroll Crafting rules it would take 4 workweeks and 5000GP to craft, the equivalent of 100lbs of gold, a vast investment of time and money. And they'd still need to succeed on a DC15 intelligence check to use the scroll, if they fail the check the 5000GP magic item is made worthless.