So killer rat swarms in D&D always seemed weirdly overpowered to me. In 5e a swarm of rats does 2d6 damage, or the equivalent of being hit by someone swinging a greatsword every six seconds. Or enough to kill an average commoner in 3 seconds. That just never seemed right to me.

So assuming they were magically compelled to attack people or something like that would a swarm of regular rats realistically be that much of a threat to a group of healthy humans trying to wade through them?

My instinct is that they've be more of a slow and painful environmental hazard than something immediately lethal (dying later of disease or blood loss is a different story).


closed as primarily opinion-based by nitsua60, daze413, Miniman, okeefe, Tritium21 Jan 17 '16 at 4:46

Many good questions generate some degree of opinion based on expert experience, but answers to this question will tend to be almost entirely based on opinions, rather than facts, references, or specific expertise. If this question can be reworded to fit the rules in the help center, please edit the question.

  • \$\begingroup\$ I've re-tagged it 5e as that's the swarm you discuss in the body. dungeons-and-dragons applies to questions that span many or all editions. If that's what you'd intended feel free to roll back my edit (click on "edited XX ago") and I'd suggest you remove the 5e-specific material from the body. \$\endgroup\$ – nitsua60 Jan 16 '16 at 22:47
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    \$\begingroup\$ Can you clarify what part of the dissonance between magical swarms and your assessment of a swarm's realistic threat isn't covered by "The Nature of Swarms" (MM p.337)? I'm not sure what the core question is here. \$\endgroup\$ – nitsua60 Jan 16 '16 at 22:49
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    \$\begingroup\$ The abstraction of hit points is probably very relevant to this question; I'd expect good answers to mention it. \$\endgroup\$ – BESW Jan 16 '16 at 22:57

This is not realistic and isn't intended to be. In many ways, this one included, D&D is not emulating reality, it's emulating fantasy fiction tropes. The trope involved here is the aptly-named Swarm of Rats:(Warning: TVTropes link)

Rodents are widely reviled, but not very threatening; after all, anyone can set a mousetrap. So how do writers make them a legitimate threat? By having a very, very large swarm of them all at once! One rat isn't scary, but a huge wave of rats eating a victim alive, one bite at a time? Horrifying.

Note the bit about writers in there: this isn't a matter of realistic rat swarms, this is about the horrifying, slavering, diseased, malevolent Evil Rats(Ditto) that live only in our cultural imaginations. (In reality, rats are one of the most intelligent and affectionate rodents.*) An unrealistically-dense and -large swarm of fantasy rats is much more dangerous than a realistically-not-dense and -not-large swarm of these adorable furballs:

enter image description here
Little big rat” by Ninisaurus licensed CC BY-SA 3.0

* Not necessarily affectionate with humans if they're wild, because that would be maladaptive! They are affectionate and intelligent compared to other rodents, regardless of domesticity, contrary to popular imaginings of various rodent temperaments. Most rodents that we think fondly of, like mice and Syrian hamsters, are actually temperamentally loners and jerks.

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    \$\begingroup\$ This answer addresses the question very well, pointing out the difference between rats in imagination and rats in reality. Bonus points for pointing out that mice are jerks! \$\endgroup\$ – Lost_in_Hyrule Jan 17 '16 at 17:33

Even in the real world, without magically enhanced beasts, Rats can chew through Steel.

Rat teeth can exert 24,000 pounds per square inch. They can chew through wood, asbestos, brick, cinder blocks, four inch thick concrete, aluminium, even a 1/2-inch thick sheet of metal.

To put this 24,000 PSI number into contrast: A Rottweiler has a bite of less than 350 PSI.
An African Lion has a bite of 691 PSI.
And the Saltwater Crocodile, which has the strongest bite of any animal today*, only has 7700 PSI.

With a little more predatory instinct, and some determination, a rat could hamstring a human in a single bite or chew through their jugular. And a swarm with hundreds of these monsters would not need to be smart, with hundreds of biting mouths they could strip the flesh from your bones like a swarm of piranha.

Rats are not a threat to humans normally, as they are not brave enough to attack one, not because a swarm would not be able to kill one.

* The apparent contradiction is based on how you measure the biting force. Rodents (from Latin "to gnaw") have by far the sharpest teeth of any animal (I am aware of), and additionally have greater control over their bite compared to any other listed here. Allowing them to focus all their force into a tiny point, while crocodiles and lions are left to crush and tear.


Swarms are an unnatural grouping of small creatures into a lethal crowd/group.

As discussed in this answer on a related question about swarms, the swarm as a thing is a case of "the whole being greater than the sum of its parts."

About Swarms:

They form as a result of some sinister or unwholesome influence ... even Druids can't charm these swarms, and their aggressiveness is borderline unnatural. (MM p. 337)

The nature of "swarming" makes a bunch of single creatures act collectively and thus pose a greater danger to a party than a few rats. Consider this: a squad of soldiers or goblins is far more dangerous than a single soldier.


The question doesnt seem to be about rules but nonetheless I'll answer it like this. There are several accounts of people killed by rats though the majority of them are infants or sick people unable to defend themselves. If you've ever startled a rat in a cornerd space you know how aggressive it will get and they could pose a threat, for example, if they are fleeing a sewerflood and you stand in their way they could attack to get away. Their instinct is to flee but they can go berserk and two hundred or so creatures of about 0,5 kilos attacking you with teeth and claws would pose an immidate threat.

  • \$\begingroup\$ The answer about rats being affectionate refers to domedticated rats aka "fancy rats" and the temperamental difference between them and wild rats (rattus rattus or rattus norvegicus) is the same as a family oriented labrador and a feral dog. \$\endgroup\$ – Ginger Jan 16 '16 at 23:34
  • \$\begingroup\$ I have never startled a rat in a cornered space. Are you speaking from experience? Additional details about your dealings with rats could add a lot to this answer. \$\endgroup\$ – Ryan Veeder Jan 17 '16 at 0:17
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    \$\begingroup\$ @RyanVeeder I once killed a cornered rat. He died with what I took to be a look of defiance in his eye. IRL, you don't get XP, you simply have to dispose of the rat without your wife getting wind of the whole event. (The weapons I used were a broom stick and a cinder block. No +1 scimitar of swiftness was available ...) \$\endgroup\$ – KorvinStarmast Jan 17 '16 at 6:10

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