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Swarm of Poisonous Snakes 5e: Stats, Venom Math and the Snake Pit
A swarm of poisonous snakes is a CR 2 Medium swarm of Tiny beasts with AC 14, 36 hit points, a 30-foot walk and swim speed, and a +6 bite. In the 2014 rules a hit deals 7 piercing damage plus 14 poison damage on a failed DC 10 Constitution save (half on a success). The 2024 rules rename it the Swarm of Venomous Snakes and make the poison automatic: every hit deals 8 piercing plus 10 poison, no save. It is the most dangerous beast swarm in the SRD, and unlike the others, its poison damage doesn't drop when the swarm is hurt.
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 snake. The swarm can't regain hit points or gain temporary hit points.
Actions
Bites.Melee Weapon Attack: +6 to hit, reach 0 ft., one creature in the swarm's space. Hit: 7 (2d6) piercing damage, or 3 (1d6) piercing damage if the swarm has half of its hit points or fewer. The target must make a DC 10 Constitution saving throw, taking 14 (4d6) poison damage on a failed save, or half as much damage on a successful one.
Stat block from the SRD 5.1 (2014 rules) by Wizards of the Coast, licensed under CC-BY-4.0. Check an encounter with this monster in the encounter calculator.
Dexterity 18 gives it AC 14 with no armor and makes Dexterity its best save (+4). 36 hit points is a lot for a swarm, and resistance to bludgeoning, piercing and slashing damage means a party of weapon users effectively has to deal 72. The bite only reaches a creature in the swarm's own space, and its piercing part drops from 2d6 to 1d6 at 18 hit points or fewer. The DC 10 save for the 4d6 poison stays the same no matter how hurt the swarm is.
Otherwise it follows the standard swarm rules in both editions: shared spaces, no healing, eight condition immunities.
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 snake. The swarm can’t regain Hit Points or gain Temporary Hit Points.
Actions
Bites.Melee Attack Roll: +6, reach 5 ft. Hit: 8 (1d8 + 4) Piercing damage—or 6 (1d4 + 4) Piercing damage if the swarm is Bloodied—plus 10 (3d6) Poison damage.
Stat block from the SRD 5.2.1 (2024 rules) by Wizards of the Coast, licensed under CC-BY-4.0. Check an encounter with this monster in the encounter calculator.
The 2024 name is new, and so is the bite. Everything else matches.
2014 Swarm of Poisonous Snakes
2024 Swarm of Venomous Snakes
CR (XP)
2 (450)
2 (450)
AC / HP
14 / 36
14 / 36
Speed
30 ft., swim 30 ft.
30 ft., swim 30 ft.
Reach
0 ft. (a creature in its space)
5 ft.
Piercing
7 (2d6), 3 (1d6) at half HP
8 (1d8 + 4), 6 (1d4 + 4) while Bloodied
Poison
14 (4d6), DC 10 Con save for half
10 (3d6), no save
Damage per hit against a character with Constitution +2 (fails the DC 10 save on a 7 or lower, 35% of the time):
Healthy swarm
Hurt swarm
2014 (7 + expected poison 9.45)
about 16.5
about 12.5
2024 (8 + 10)
18
16
The 2024 swarm hits a little harder on average and much more reliably. A good Constitution save doesn't help any more, and Bloodied barely slows it down. The 2014 swarm rewards high-Constitution characters and punishes the wizard.
How Swarms of Poisonous Snakes Fight
Each round, one big bite. At +6 against AC 16, the bite hits on a 10 or better, 55% of the time. That's about 9 damage per round for a 2014 swarm and about 10 for a 2024 swarm, and the swarm keeps up almost all of that even when Bloodied. Two swarms on one level 3 character can drop it in two rounds.
Water is cover. Swim 30 matches its walking speed. In a flooded temple, a marsh or a river ford, the swarm moves through water where characters slow down (swimming without a Swim Speed costs extra movement in both editions). Let it come out of the water and go back in.
2014: crawl in, stay in. Its reach is 0, so the 2014 swarm has to enter a target's space, which counts as difficult terrain. With 30 feet of movement that's rarely a problem. Once it's in, any character who steps out provokes an Opportunity Attack that carries the full poison damage.
2024: bite from the floor. With 5-foot reach, the 2024 swarm doesn't need to share a space. It can sit in a doorway and bite whoever steps through.
Pick the frail. Snakes go for warmth and movement, which at the table means whoever moves into their area first. In 2014, target the low-Constitution character. In 2024 it doesn't matter, so go for the lowest AC.
No retreat. Intelligence 1. The swarm fights until it dies or nothing living is left nearby.
Running a Snake Swarm Encounter
Each swarm is worth 450 XP. Encounters for four characters:
The 2014 labels come from our encounter calculator, which uses the 2014 Dungeon Master's Guide thresholds and group multiplier.
A single swarm against a level 1 party is too much. Its 36 hit points take a level 1 party of weapon users several rounds to grind through, and each round the swarm deals around 9. Use it from level 2, and at level 1 use individual poisonous snakes instead.
Snakes pair naturally with a snake-themed boss. A medusa's lair with two swarms in the ruins makes the party choose between looking around and watching the floor.
How Players Beat a Swarm of Poisonous Snakes
•Not Dexterity saves. At +4, the swarm makes Dexterity saves often. Fireball (8d6, average 28) on a failed save leaves it on 8 hit points, and on a success deals only 14. Pick Constitution (+0) or Wisdom (+0) spells.
•Spirit Guardians and Moonbeam.Spirit Guardians (3d8, Wisdom save) halves its speed and damages it every turn it stays near the cleric. Moonbeam (2d10 radiant, Constitution save) can be moved back onto it each turn as it crawls, at the cost of an action (a Magic action in 2024).
•Poison resistance helps. In both editions dwarves resist poison damage, which takes half off the biggest part of the bite. In 2014, dwarves also have Advantage on the save. Put the dwarf in front.
•Get it out of the water. The swarm doesn't resist fire, but anything underwater has Resistance to Fire damage in both editions, so wait for it to come ashore before casting Burning Hands.
•Weapons still work, slowly. Halved weapon damage adds up. A level 3 party of four weapon users deals around 10 to it per round after resistance, so expect three or four rounds.
•Healing, then distance. A character bitten twice is in trouble. Healing Word from range keeps them standing. Climbing onto a table, a statue or a ledge buys time: the swarm has no climb speed, so climbing costs it double movement, and a sheer surface may need a Strength (Athletics) check it's bad at. Against a 2024 swarm, stand at least 10 feet up or its 5-foot reach still finds you.
Snake Swarm Encounter Ideas
The offering pit. In a ruined temple, the altar sits on a platform above a pit full of snakes. The relic the party needs is on the altar. The platform's walls are sheer and smooth, so the swarm can't climb up, but the only bridge to it is a crumbling stone beam, and anyone who falls lands among the snakes. One swarm, one beam, and some careful Athletics checks.
The flooded cellar. A merchant's cellar flooded after a storm, and snakes came in with the water. The merchant needs a strongbox from the bottom. Two swarms swim in knee-deep water, and the party can't see the floor. A level 3 party that tries to wade straight in will regret it.
The snake charmer. A traveling performer's baskets hold more than one snake. When the town guard tries to arrest her for theft, she kicks the baskets over and a swarm spills into the crowded market square. The party has to protect bystanders, catch a thief and avoid the swarm, all at once.
Frequently Asked Questions
What CR is a swarm of poisonous snakes?
CR 2, worth 450 XP. It has AC 14, 36 hit points and a speed of 30 feet with a 30-foot swim speed in both the 2014 and 2024 rules.
What is the swarm of venomous snakes?
It's the 2024 name for the swarm of poisonous snakes. The stats are the same except the bite: the 2024 version has 5-foot reach and deals 8 piercing plus 10 poison damage with no saving throw.
Does a swarm of poisonous snakes poison you?
It deals poison damage but doesn't give the Poisoned condition in either edition. In 2014 a DC 10 Constitution save halves the 14 poison damage; in 2024 the 10 poison damage is automatic.
Is a swarm of poisonous snakes resistant to magic weapons?
Yes. Its resistance to bludgeoning, piercing and slashing damage has no "nonmagical" qualifier, so a magic sword is halved too. Fire, cold, radiant and other damage types work normally.
What level should a party be to fight a swarm of poisonous snakes?
Level 2 or higher. One swarm is a Moderate fight for four level 2 characters under the 2024 rules. At level 1, its 36 hit points and big poison bite make it a likely character death.
Stat blocks: System Reference Document 5.1 (2014) and 5.2.1 (2024), Wizards of the Coast, CC-BY-4.0. Tactics, encounter math and ideas are Loreify's own.
This page includes material from the System Reference Document 5.1 and 5.2.1 by Wizards of the Coast LLC, available under the Creative Commons Attribution 4.0 International License. Loreify is not affiliated with Wizards of the Coast.