A swarm of little creatures carpets the effects area,
viciously attacking all other creatures there. (Roll on the table
below to see what sort of creature is summoned.) A creature in
the swarm who takes no actions other than fighting off the
creatures takes 1 point of damage on its turn. A creature in the
swarm who takes any other action, including leaving the swarm,
takes 1d4 points of damage +1 point per three caster levels.
Spellcasting or concentrating on spells within the swarm is
1d20 Swarm Type*
18 Rats (animals)
914 Bats (animals)
1516 Spiders (vermin, poisonous)
1718 Centipedes (vermin, poisonous)
1920 Flying beetles (vermin)
*The creature types (in parentheses) indicate what sorts of
spells and effects might aid a subject against the swarm.
A swarm of poisonous creatures deals no damage to creatures
who are immune to poison, though it still prevents spellcasting
and concentration. The creatures attacks are nonmagical.
Damage reduction, being incorporeal, and other special abilities
also make a creature immune to damage from the swarm.
The swarm cannot be fought effectively with weapons, but fire
and damaging area effects can force it to disperse. The swarm
disperses when it has taken a total of 2 hit points of damage per
caster level from these attacks. Certain area or effect spells,
such as gust of wind and stinking cloud, disperse a swarm
immediately if appropriate to the swarm summoned. (For example,
only fliers are affected by a gust of wind.)
The swarm is stationary once summoned. A druid caster,
however, can (as a move-equivalent action) direct the swarm to
move up to 30 feet per round (or 90 feet per round if she has
summoned bats or beetles).