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System Reference Document 5.2.1
Swarm of Piranhas
Medium Swarm of Tiny Beasts, Unaligned
AC 13  Initiative +3 (13)
HP 28 (8d8 − 8)
Speed 5 ft., Swim 40 ft.
MOD SAVE MOD SAVE MOD SAVE
Str 13 +1 +1 Dex 16 +3 +3 Con 9 −1 −1
Int 1 −5 −5 WIS 7 −2 −2 Cha 2 −4 −4
Resistances Bludgeoning, Piercing, Slashing
Immunities Charmed, Frightened, Grappled, Paralyzed, 
Petrified, Prone, Restrained, Stunned
Senses Darkvision 60 ft.; Passive Perception 8
Languages None
CR 1 (XP 200; PB +2)
Traits
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 piranha. 
The swarm can’t regain Hit Points or gain Temporary 
Hit Points.
Water Breathing. The swarm can breathe only 
underwater.
Actions
Bites. Melee Attack Roll: +5 (with Advantage if the 
target doesn’t have all its Hit Points), reach 5 ft. Hit: 8 
(2d4 + 3) Piercing damage, or 5 (1d4 + 3) Piercing dam-
age if the swarm is Bloodied.
Swarm of Rats
Medium Swarm of Tiny Beasts, Unaligned
AC 10  Initiative +0 (10)
HP 14 (4d8 − 4)
Speed 30 ft., Climb 30 ft.
MOD SAVE MOD SAVE MOD SAVE
Str 9 −1 −1 Dex 11 +0 +2 Con 9 −1 −1
Int 2 −4 −4 WIS 10 +0 +0 Cha 3 −4 −4
Resistances Bludgeoning, Piercing, Slashing
Immunities Charmed, Frightened, Grappled, Paralyzed, 
Petrified, Prone, Restrained, Stunned
Senses Darkvision 30 ft.; Passive Perception 10
Languages None
CR 1/4 (XP 50; PB +2)
Traits
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 rat. The swarm 
can’t regain Hit Points or gain Temporary Hit Points.
Actions
Bites. Melee Attack Roll: +2, reach 5 ft. Hit: 5 (2d4) 
Piercing damage, or 2 (1d4) Piercing damage if the 
swarm is Bloodied.
Swarm of Ravens
Medium Swarm of Tiny Beasts, Unaligned
AC 12  Initiative +2 (12)
HP 11 (2d8 + 2)
Speed 10 ft., Fly 50 ft.
MOD SAVE MOD SAVE MOD SAVE
Str 6 −2 −2 Dex	14 +2 +2 Con 12 +1 +1
Int	5 −3 −3 WIS 12 +1 +1 Cha 6 −2 −2
Skills Perception +5
Resistances Bludgeoning, Piercing, Slashing
Immunities Charmed, Frightened, Grappled, Paralyzed, 
Petrified, Prone, Restrained, Stunned
Senses Passive Perception 15
Languages None
CR 1/4 (XP 50; PB +2)
Traits
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 raven. The swarm 
can’t regain Hit Points or gain Temporary Hit Points.
Actions
Beaks. Melee Attack Roll: +4, reach 5 ft. Hit: 5 (1d6 
+ 2) Piercing damage, or 2 (1d4) Piercing damage if the 
swarm is Bloodied.
Cacophony (Recharge 6). Wisdom Saving Throw: DC 
10, one creature in the swarm’s space. Failure: The 
target has the Deafened condition until the start of the 
swarm’s next turn. While Deafened, the target also has 
Disadvantage on ability checks and attack rolls.
Swarm of Venomous Snakes
Medium Swarm of Tiny Beasts, Unaligned
AC 14  Initiative +4 (14)
HP 36 (8d8)
Speed 30 ft., Swim 30 ft.
MOD SAVE MOD SAVE MOD SAVE
Str 8 −1 −1 Dex 18 +4 +4 Con 11 +0 +0
Int 1 −5 −5 WIS 10 +0 +0 Cha 3 −4 −4
Resistances Bludgeoning, Piercing, Slashing
Immunities Charmed, Frightened, Grappled, Paralyzed, 
Petrified, Prone, Restrained, Stunned
Senses Blindsight 10 ft.; Passive Perception 10
Languages None
CR 2 (XP 450; PB +2)