Цитата
Swarm Subtype: A swarm is a collection of Fine, Diminutive, or Tiny creatures that acts as a single creature. A swarm has the characteristics of its type, except as noted here. A swarm has a single pool of Hit Dice and hit points, a single initiative modifier, a single speed, and a single Armor Class. A swarm makes saving throws as a single creature.
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Traits: A swarm has no clear front or back and no discernable anatomy, so it is not subject to critical hits or flanking. A swarm made up of Tiny creatures takes half damage from slashing and piercing weapons. A swarm composed of Fine or Diminutive creatures is immune to all weapon damage. Reducing a swarm to 0 hit points or lower causes it to break up,
though damage taken until that point does not degrade its ability to attack or resist attack. Swarms are never staggered or reduced to a dying state by damage. Also, they cannot be tripped, grappled, or bull rushed, and they cannot grapple an opponent. A swarm is immune to any spell or effect that targets a specific number of creatures (including single-target spells such as disintegrate), with the exception of mind-affecting effects (charms, compulsions, phantasms, patterns, and morale effects) if the swarm has an Intelligence score and a hive mind. A swarm takes half again as much damage (+50%) from spells or effects that affect an area, such as splash weapons and many evocation spells
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Swarms made up of Diminutive or Fine creatures are susceptible to high winds such as that created by a gust of wind spell. For purposes of determining the effects of wind on a swarm, treat the swarm as a creature of the same size as its constituent creatures (see Winds, page 95 of the Dungeon Master’s Guide). For example, a swarm of locusts (a swarm of Diminutive creatures) can be blown away by a severe wind. Wind effects deal 1d6 points of nonlethal damage to a swarm per spell level (or Hit Dice of the originating creature, in the case of effects such as an air elemental’s whirlwind).
A swarm rendered unconscious by means of nonlethal damage becomes disorganized and dispersed, and does not reform
until its hit points exceed its nonlethal damage.
Swarm Attack: Creatures with the swarm subtype don’t make standard melee attacks. Instead, they deal automatic damage to any creature whose space they occupy at the end of their move, with no attack roll needed. Swarm attacks are not subject to a miss chance for concealment or cover. A swarm’s statistics block has ”swarm” in the Attack and Full Attack entries, with no attack bonus given Swarms do not threaten creatures in their square, and do not make attacks of opportunity with their swarm attack. However, they distract foes whose squares they occupy, as described below.
Говоря вкратце - рои не делают AOO никогда, равно как не угрожают клеткам. Они просто автоматически атакуют существ, на клетках которых стоят, причем тут не помогает cover, concealment и прочие ухищрения.
Рои не могут быть сбиты с ног, захвачены (в grapple), сдвинуты с места bull rush-ем и так далее. На них не действуют заклинания, имеющие целью отдельных существ (исключение - действующие на разум, если у роя есть hive mind), зато заклинания и эффекты, бьющие по области наносят им полуторный урон, и рой уязвим для сильного ветра - фактически, рой из Diminutive существ сдувается так же просто, как и одно Diminutive существо. Даже не сдувая, ветер наносит им нелетальный урон (унося отдельных существ и дезорганизуя рой). Рои Fine or Diminutive существ неуязвимы для оружия, Tiny - получают половинный урон от колющего и режущего.
Есть еще тонкости с роями нежити и изгнанием, но это вам, вроде, ни к чему?