Is a Raging Barbarian immune to 1-damage attacks?

Question

A Raging Barbarian has resistance to certain types of damage. An unarmed strike by a class with 0 Strength, for example, does 1 point of damage (not talking about Monk's unarmed strike, just a regular punch).

Does the Barbarian's resistance make him immune to 1-damage attacks? Since the damage is halved and rounded down. Or is there a minimum damage value (namely, 1) that cannot be resisted?

I'm asking because I've decided to create a plague of flesh-eating scarabs, with 1HP and that do 1 point of damage. However, there are hundreds of them, the PCs will have to stay of out reach and use low-level AoEs or simply escape from them. These scarabs do damage by being in contact with enemies, no Attack Roll required, but I don't want the Barbarian do be immune to it.

Answer 1

Alas, there is no minimum damage value. From page 10 of the Sage Advice Compendium:

Can damage be reduced to 0 by resistance or another form of damage reduction? There is no damage minimum in the rules, so it is possible to deal 0 damage with an attack, a spell, or another effect.

Therefore, due to the Round Down rule, the raging barbarian wouldn't be immune in the sense of game mechanic terminology but they would take 0 damage from something that only does 1 point of damage of a type that the barbarian is resistant to.

Answer 2

Only if the damage type is bludgeoning, piercing, or slashing.

Under the assumption that the 1 point of damage is bludgeoning, piecing, or slashing, yes the Barbarian would be effectively immune to it because resistance causes damage of one of the listed types to be divided in half and then rounded down. Since there is no minimum damage in 5e then the damage would be reduced to 0 points.

However, to circumvent this, just make the damage type be necrotic or another suitable type that raging Barbarians do not have resistance against. (This only covers the Barbarian's Rage feature, not any features that may add additional resistances, such as the Bear Totem feature.) Then it would deal 1 point of damage even to the raging Barbarian.

Answer 3

Your are correct in your surmise, the rules you quote do allow the raging barbarian to ignore the scarabs... However—

The solution can be found within your problem.

I.e. you are creating your own problem (a custom monster that cannot affect the barbarian), when your intent is to create a monster that is effective against everyone. If you control the conditions that the monster operates under, you also control the exceptions. Simply write a description like:

Bite. melee weapon attack. +2 to hit, reach 0 ft. (must occupy same space as target), one target. Hit: 1 (1 point) piercing damage. This damage cannot be reduced by resistances, however immunity to piercing damage still protects the target.

This is not cheating in any way, merely an exercise of the 5e principle of specific overriding general in order to create a monster that fulfills the campaign niche you want to fill (a nuisance that can potentially be deadly to anybody in large enough numbers.)

This principle is found everywhere within the system. It's even there in the barbarian himself, whose specific class-based resistance overrides general damage rules.

Answer 4

Letting the barbarian be immune to 1-damage attacks while raging is relatively harmless. A barbarian's typical playstyle in similar situations (Spike Growth etc.) is to wade through the danger. Additionally, they wouldn't be immune for the WHOLE campaign, just for 2-6 minutes a day as they rage, with no AOE available to them. You're nerfing a player who's character should be able to do just that, fight swarms of enemies that do 1 piercing damage (spiders, mice, etc.) taking nothing.