D&D 3E/3.5 Damaging swarms (3.5)

[Alexander123]

When you attack a swarm with an improvised weapon such as a torch for instance, do you add strength when calculating damage?

 

[Pergentile]

A torch deals 1d3 points of fire damage, not physical damage, and so the elemental damage is not modified by your strength modifier. If the torch does physical damage too, like 1d4, then your strength modifier would be applied as normal.
A swarm of creatures is considered to be a single creature, and the creatures in the swarm are packed so closely together that they are effected by physical forces just as a regular creature of the same size would.

You swing a sword? It does damage as normal. Shoot an arrow into the swarm? The same. Either of those happen to be flaming? Bonus damage.

 

[NaturalFn20]

You actually have to check the particular swarm in question. Some swarms like centipede swarms, bat swarms, spider swarms, locust swarms etc are immune to physical damage.

Some swarms like rat swarms take half damage from slashing and piercing weapons or have DR 10/magic. Look at swarm characteristics and also each individual type of swarm.

That said, if it's immune to physical damage, your weapon and strength bonus have no affect on it. These swarms are annoying and the only way to kill them is an AoE spell or energy (fire etc).