"Hold,” the rogue said. The entire party stopped behind him in the middle of the spiral staircase.
“What’s the holdup?” the fighter asked. A less-than-subtle note of irritation colored her voice. “You’re not telling us that the necromancer trapped her own tower staircase? The one that she uses daily?”
The rogue shot her a nasty glare and held out a finger to silence her. He turned his gaze back up the stairwell. His flat nose twitched and his black eyes began to water. “Do you smell that?” he asked.
“Now that you mention it, I do,” the wizard said. He shuffled his small gnomish body past the fighter and emerged next to the rogue. “An alchemical smell, perhaps? Some form of chemical compound, a bleaching agent, perhaps? Lye… or some derivative, I suspect.”
The rogue’s eyes widened, and he took an involuntary step backward. “Everyone off the staircase,” he muttered. He whirled around to look at his party, panic scrawled across his face. “Everyone back! Now!”
The heavily armored dwarf cleric in the back rank began fumbling to turn about in the cramped stairwell, and the fighter nimbly leapt over him, taking the stairs three at a time. The rogue stooped and grabbed the gnome wizard by his hood and slung him onto his shoulder. The wizard looked back up the staircase as the party fled, and felt a tingle of magic along his white whiskers. A second later, he saw it: the cloud of thick, yellow-green gas billowing rapidly down the staircase behind him.
“Oh! Oh my!” the wizard gasped. The gas surged into his face and he felt a terrible stinging as he screwed his eyes shut. His mustache shriveled and disintegrated as the caustic gas ate away at its bristles. He threw his cloak around his face and turned to face forward. “Run, everyone!” he coughed. “It’s a cloudkill! Cloudkill!”
I really used cloudkill like a dummy last week. My suboptimal use of cloudkill was sort of purposeful—it was in a fight I wanted the characters to win—but it was also due to my own half-remembered understanding of the spell rules. Once I flipped away from my monster’s stat block and actually read the spell as written in the Player’s Handbook, I felt a little twinge of regret for so royally mucking up my lich’s strategy.
I didn’t worry about it too much, because it was still an exciting fight on the whole, but I still feel like I could have made it even better if I fully understood how cloudkill worked before I committed to using it.
What Does Cloudkill Do?
As a 5th-level spell, cloudkill had better be packing some serious punch. It comes with four main effects:
- Initial area-of-effect damage. While cloudkill doesn’t deal damage instantaneously upon casting, like a fireball, it does require all creatures within its 20-foot-radius area to make a Constitution save at the start of each of their turns, taking 5d8 poison damage on a failed save or half as much on a successful one. This almost guarantees that every creature in the spell’s area will take damage.
- Obscuration. This is an easy rule to overlook, but the cloud’s entire area is heavily obscured. All creatures within the cloud are blinded. As usual, creatures with blindsight suffer no vision penalties while blinded.
- Ongoing effects. The cloud lingers on the battlefield, continuing to deal damage and obscure vision, as long as its caster maintains concentration.
- Movement. The caster can’t move the cloud directly, but it does move on its own. At the start of each of the caster’s turns, the cloud moves 10 feet away from the caster, “rolling along the surface of the ground.” The cloud is heavier than air, so it sinks to the ground and even passes through holes or grates in the ground.
So, how does cloudkill measure up? Its initial damage isn’t anything to write home about. A mere 5d8 poison damage is less than a fireball. (The average of 5d8 is 23, the average of 8d6 is 28.) So, in order for cloudkill to out-damage a spell two levels lower than it, it needs to deal damage on at least two turns.
This isn’t easy on most battlefields. The cloud’s radius is only 20 feet, so a creature with 30 feet of movement always has at least one way of escaping the cloud’s area. This problem is only exacerbated by the fact that the cloud automatically moves 10 feet away from the caster on their turn, making it challenging to keep the cloud centered on your enemies, especially if they are charging right at you. All this is to say nothing of the many creatures who resist or ignore damage; most (if not all) undead and fiends (and a smattering of other creatures) are completely immune to poison damage. It also has the troubling weakness of being able to be dispersed by strong wind, such as those created by the 2nd-level spell gust of wind.
All this to say, while cloudkill may look like another area-of-effect damage spell, its actual applications are much subtler. I made the mistake of using it like a fireball in my home game last week, and while it did a nice chunk of damage to the entire party, it was relatively unimportant in the grand scheme of things. If I had planned a bit better, cloudkill could have devastated the party. Why?
Cloudkill is a Combo Spell
While cloudkill is relatively underwhelming on its own, it is not without its uses. Just like constructing a combo in card games like Magic: the Gathering or Hearthstone, individual spells that may seem underpowered can create a truly nightmarish scenario when played in tandem. Here are some combos that turn cloudkill from a C-list spell into a grade-A monster-killer. (Or player character-killer, depending on which side of the DM screen you prefer to play from!)
Comboing Cloudkill as a Player
Since cloudkill requires your concentration, creating combinations with your own spells can be difficult. However, if you’re playing a sorcerer or wizard (or bard who has learned cloudkill through their Magical Secrets feature), you should try teaming up with another spellcaster in your party to discover wicked spell combinations.
Cloudkill works best when you have an environmental advantage. This could mean that you have the high ground and the enemies have to climb to reach you (such as up a cliff or staircase), or it could mean that your enemies are caught in a space with little room to maneuver, such as a box canyon or a dungeon corridor. Since an area’s environment is typically dictated by the Dungeon Master, you’ll need to find other options. This could involve you manipulating the environment with magic, finding ways to hold your enemies in place, or controlling their movements. Here are some strategies and sample combos:
- Encaging. By trapping your foes within a magical cage, you can both keep yourself safe from their attacks and trap them inside your cloudkill’s radius. Wall of force is the gold standard as far as this combo is concerned, though wall of stone is a useful alternative with a larger area of effect. Since this spell requires concentration, you’ll unfortunately need two spellcasters of 9th level or higher to pull this combo off. Forcecage provides an even more reliable version of this combo and doesn’t require concentration, though it does consume a valuable 7th-level spell slot.
- Immobilizing. By preventing your foes from moving, you can trap them in the cloud—until it rolls away from them, anyway. A grappled creature can’t move, so a strong character willing to take some poison damage (or who is resistant to poison, like a dwarf, or immunized to poison damage, such as through a druid’s Elemental Wild Shape) can wade into the cloud and hold them down. Restrained creatures, such as through the ensnaring strike spell are also immobilized, and creatures that are paralyzed by spells like hold person are also at the mercy of the cloudkill. Try having a fellow spellcaster cast hold person at a higher level to paralyze even more of your enemies!
- Forced Movement. Since cloudkill deals damage when a creature starts its turn in the cloud and the first time on a turn that it enters the cloud’s radius, your allies can use abilities that force enemies to move to hurl them into the cloud. Such effects include command, fear, thunderous smite, thunderwave, the warlock’s Repelling Blast or Grasp of Hadar (Xanathar’s Guide to Everything) invocations, or even the good old-fashioned Shove action. A well-coordinated party could play ping-pong with an enemy, pushing them into the cloud, dragging them out, and pushing them back in again for massive damage every turn… though your DM probably won’t be too happy seeing their fearsome baddie turned into a glorified shuttlecock.
Comboing Cloudkill as a Dungeon Master
Dungeon Masters have a lot more ways to realize cloudkill’s true destructive potential than their players do, since they have the power to design encounter environments and have the benefit of gearing the monsters’ abilities towards a specific encounter. They also have the major advantage of being able to stack the deck by filling encounters with dozens of minions to keep their cloudkill-casting masters safe from harm. While Dungeon Masters using cloudkill should try to immobilize enemies, move them about, and trap them just like players do, they have many different options at their disposal. Here are just a few ways you can do this as a Dungeon Master, and even a few DM-specific options:
- Creating Advantageous Battlefields. As the DM, you can design the terrain of your encounter area. While terrain isn’t factored into the math of the Challenge Rating system, giving your enemies advantageous terrain can seriously impact the difficulty of an encounter. Since cloudkill drifts downward, a spellcaster at the top of a 30-foot-high (or higher) cliff can cast the spell, causing it to drift down and deal damage over multiple turns as the characters attempt to scale the cliff. Or, perhaps the fight takes place in a natural crater; the villain hides high above the crater, but projects a major image of their form in the pit. Then, when the characters enter the deep crater, the villain cackles, dispels the illusion, and casts cloudkill within the high-walled pit.
- Spellcasting Allies. Cloudkill’s troublesome concentration requirement is less troublesome to DMs than it is to players. Just add a mage to your combat encounter, deck them out with mage armor and a shield spell, and have them prepare spells to either encage the characters like wall of force or wall of stone, or to immobilize them like hold person. Heck, do both! This extra spellcaster’s entire job is to stop the party after their master casts cloudkill and then hide so that their concentration can’t be disrupted by any allies that escape the deathtrap. Adjust your perception of the encounter difficulty accordingly, of course. This mage won’t be hurling fireballs (probably), but being able to spring this kind of ruthless trap on your characters is even more deadly than a fireball or two.
- Undead Allies. Cloudkill is a potent spell in the hands of a villainous necromancer, a spellcasting vampire (see the variant vampire options in the Monster Manual!), or a lich because these powerful spellcasters tend to bring their undead minions as backup. Since the undead are immune to cloudkill’s poison damage, they can wade into the cloud and attack the players with impunity. Imagine a cloudkill surrounding the players, a wall of stone rising up around them, and then a horde of shrieking vampire spawn scaling the wall! Similarly, a warlock of the Fiend could bring along some poison-immune demons or devils to do the same, and a transmuter could bring along a golem or other constructs.
Create your own Combos
These clever uses of cloudkill are only the tip of the iceberg when it comes to this spell. What are some other ways you can use this spell to wreak havoc upon your players’ characters—or your DM’s monsters? There are certainly ways unique to your own party—perhaps instead of a wall of stone, your party wizard knows Evard’s black tentacles and can use that to restrain your targets while you enwreathe them in noxious fumes. Planning combination moves with your party members is one of the best parts of D&D, and one I rarely see utilized. Party-wide plans of attack happen all the time, but intra-party combos? That’s something that will really make you stand out from the crowd.
James Haeck is the lead writer for D&D Beyond, the co-author of Waterdeep: Dragon Heist and the Critical Role Tal'Dorei Campaign Setting, and is also a freelance writer for Wizards of the Coast, the D&D Adventurers League, and Kobold Press. He lives in Seattle, Washington with his partner Hannah and his two stinky kitties, Mei and Marzipan. You can usually find him wasting time on Twitter at @jamesjhaeck.