Keen Smell. The swarm has advantage on Wisdom (Perception) checks that rely on smell.
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 Weapon Attack: +2 to hit, reach 0 ft., one target 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.
How many swarms of rats for a fight?
A swarm of rats is worth 50 XP. Using the 2024 encounter budgets (SRD 5.2), this is how many swarms of rats fit each difficulty for a party of four characters of the same level. A dash means even one would be over the budget.
Party level
Low
Moderate
High
1st
4
6
8
2nd
8
12
12+
3rd
12
12+
12+
Budgets add up every monster’s XP, so you can swap some for other creatures of the same total. Try other party sizes and mixes in the encounter calculator.
How the swarm of rats compares at CR 1/4
Against the 31 other challenge 1/4 monsters in the SRD 5.1, the swarm of rats has more hit points than 30 of them, which makes it one of the toughest at its CR. See every CR 1/4 monster.
Statistic
Swarm of Rats
CR 1/4 average
Armor Class
10
11.8
Hit points
24
15
Best attack bonus
+2
+4
Swarm of Rats 2024 stat block
The 2024 Monster Manual revised the swarm of rats, and the SRD 5.2 carries the new stat block. What changed:
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.
