Last week, I talked about the basic rules that swarms of smaller creatures have in many systems. Today, I wanted to give you a neat reskinning trick! You can turn lots of monsters into swarms by overlaying the swarm rules on top of an existing stat block.  

Let’s start with a new D&D 5E monster, a swarm of acid wasps! These nasty, intelligent critters lurk in acid pools, deadly swamps, and caustic areas throughout the lower planes. They’re malicious and durable individually, and together they form into a flying, acid-spewing cloud.

Acid Wasp Swarm

Large swarm of tiny fiends, chaotic evil

Armor Class 18 (natural armor) 

Hit Points 127 (15d10 + 45) 

Speed 40 ft., fly 80 ft., swim 40 ft.

STR      DEX     CON     INT     WIS     CHA

10 (+0) 14 (+2) 17 (+3) 12 (+1) 11 (+0) 15 (+2)

Skills Perception +6, Stealth +5

Damage Immunities acid

Damage Resistances bludgeoning, piercing, and slashing

Condition Immunities charmed, frightened, paralyzed, petrified, prone, restrained, stunned

Senses blindsight 30 ft., darkvision 120 ft., passive Perception 16

Languages understands Common but can’t speak 

Challenge 7 (2,900 XP)

Amphibious. The acid wasp swarm can breathe air and water.

Swarm. The swarm can occupy another creature’s space and vice versa, and the swarm can move through any opening large enough for a Tiny acid wasp (which is about the size of a pigeon). The swarm can’t regain hit points or gain temporary hit points.


Multiattack. The acid wasp makes three attacks with its stings.

Stings. Melee Weapon Attack: +7 to hit, reach 0 ft., one target in the swarm’s space. Hit: 10 (3d6) piercing damage plus 4 (1d8) acid damage, or 7 (2d6) piercing damage plus 2 (1d4) acid damage if the swarm has half its hit points or fewer.

Acid Spew (Recharge 5–6). The swarm spews acid in a 30-foot line that is 5 feet wide. Each creature in that line must make a DC 14 Dexterity saving throw, taking 49 (11d8) acid damage on a failed save, or half as much damage on a successful one. 


This isn’t really a new monster, as you might have guessed. It’s a young black dragon stat block with the D&D 5E swarm abilities overlaid on top of it. I dropped its Strength, averaged its bite/claw/claw damage into a single stings attack, and I replaced its many good saving throws with a swarm’s typical resistances and immunities. But that’s it. 


Let’s do it again!
Here’s a new Starfinder monster, one that plagues starships, power plants, and other electrical systems throughout the galaxy. Individually, shockworms aren’t too threatening; the size of a human thumb, they mindlessly devour electrical impulses and produce startling but harmless electrical jolts to warn prey away. They reproduce rapidly and form into shockworm swarms, which ramp up in intelligence considerably to form a hivemind. Shockworm swarms understand technology and, when working together, cunningly reroute energy pulses to devour.

Shockworm Swarm CR 3

XP 800

N Large magical beast (swarm)

Init +1; Senses darkvision 60 ft., electrolocation, low-light vision; Perception +8


HP 35; RP 3

EAC 14; KAC 15

Fort +4; Ref +4; Will +6

Defensive Abilities swarm defenses; Immunities poison, swarm immunities; Resistances electricity 5


Speed 20 ft.

Melee swarm attack (1d4+4 P)

Ranged electrical discharge +8 (1d4+3 E)

Space 10 ft.; Reach 0 ft.

Offensive Abilities distraction (DC 14), semiconductive


Str +1; Dex +1; Con +2; Int +4; Wis +0; Cha -1

Skills Computers +13, Engineering +13, Life Science +8, Physical Science +8, Stealth +13

Languages Common; telepathy 100 ft. (can’t speak any language)


Environment any

Organization solitary, pair, or dielectric (3–5)

Special Abilities

Electrical Discharge (Ex) A shockworm swarm can release a small bolt of electricity at a single foe as a ranged attack with a range increment of 40 feet.

Electrolocation (Ex) A shockworm swarm in contact with a crystalline or metallic surface can detect the presence of other creatures within 60 feet that are also in contact with the same surface, even through walls and other obstacles. This otherwise functions as blindsense (vision).

Semiconductive (Ex) Shockworms swarms can alter their silicon-based composition to increase or decrease their electric conductivity. As a move action, a shockworm swarm can spend 1 Resolve Point and lose its natural resistance to electricity for 1 round to gain a bonus to the damage it deals with its electrical discharge ranged attack equal to its Constitution modifier. These effects last until the beginning of its next turn.


For this, I’ve lightly altered a urog, an intelligent electrical-themed monster. In addition to giving it the swarm subtype and swarm abilities, I swapped out a skill that didn’t seem relevant. The only thing I had to look up was what it’s swarm damage should be, but that’s a pretty easy calculation to pull off of a table in the Alien Archive


Okay, one more, this time from Pathfinder Second Edition. One of the strangest gods of the mysterious realm of the fey is Shadowfeaster, an evil deity of hunger, accidents, and twilight. Shadowfeaster’s most numerous minions are gloamlings, tiny weasel-like people wrapped in shadow. Only six inches tall even when not hunched over, gloamlings like to travel in close packs for protection—as many other creatures of the fey realm find them tasty—and to more easily play malevolent pranks on larger creatures.

Gloamling Swarm     Creature 12

Uncommon, LE, Large, Fey, Swarm

Perception +21; hungersense (imprecise) 30 feet, low-light vision

Languages Aklo, Common, Sylvan

Skills Crafting +23, Deception +25, Nature +21, Stealth +25, Thievery +25

Str -4, Dex +7, Con +4, Int +5, Wis +3, Cha +4

Hungersense Hungersense allows the gloamling swarm to sense creatures that require food to live.

AC 34; Fort +22, Ref +25, Will +19

HP 235; Immunities precision, swarm mind; Weaknesses area damage 10, cold iron 10, splash damage 10; Resistances physical 10 (except cold iron)

Treacherous Aura (aura, primal, transmutation) 15 feet. Tangled roots, jagged divots, sharp rocks and other hazards appear on surfaces in the aura, creating difficult terrain.

Trip Up [reaction] Trigger A creature critically fails a melee attack to hit the gloamling swarm or moves into a space within the swarm’s treacherous aura; Effect The triggering creature must attempt a DC 32 Reflex save.

Critical Success The target is unaffected.

Success The target is flat-footed until the start of its next turn.

Failure The target takes 2d10 bludgeoning damage and is flat-footed until the start of its next turn.

Critical Failure As failure, and the target is knocked prone.

Speed 30 feet; trickster’s step

Grabbing Claws [one-action] Each enemy in the swarm’s space takes 5d8 slashing damage (DC 32 basic Reflex save). On a failed saving throw, the gloamling swarm also knocks a held or carried weapon to the ground in the target’s space.

Change Shape [one-action] (concentrate, polymorph, primal, transmutation) The gloamling swarm changes into its natural form or that of any emaciated humanoid. It remains a swarm, however, and creatures within its humanoid form are subjected to its grabbing claws.

Trickster's Step The gloamling swarm ignores difficult terrain and doesn’t trigger traps with its movement.


This one was, originally, a fey creature called a gimmerling. In addition to adding on swarm rules (which meant adding some resistances and weaknesses; I just used the same value for those as for its existing cold iron weakness), I took away its items and its Sneak Attack ability. I dropped its Strength score by quite a bit, since very strong little critters didn’t make sense to me, but I kept its other ability scores the same. I had to create a swarm attack for it, and I eyeballed the damage as the amount it would otherwise do with its items and Sneak Attack that I took away. That seems to work fine. Its Disarm ability seemed tough to keep, mechanically speaking, so I just folded it in with its swarm attack—fail that save, and the disarm happens, too. I thought about eliminating the creature’s Change Shape ability, but a swarm that can change shape into a person seems pretty creepy to me. This one was the most fun of these three new monsters to make!


Now you’ve got some rules and some examples—you can make up swarms of swarms of your own!