Vulnerabilities Of Swarms
Swarms are extremely difficult to fight with physical attacks. However, they have a few special vulnerabilities, as follows:
A lit torch swung as an improvised weapon deals 1d3 points of fire damage per hit.
A weapon with a special ability such as flaming or frost deals its full energy damage with each hit, even if the weapon’s normal damage can’t affect the swarm.
A lit lantern can be used as a thrown weapon, dealing 1d4 points of fire damage to all creatures in squares adjacent to where it breaks.
问题核心其实还是一个官方没讲明白的问题。集群免疫的那个说明是【spell or effect that targets a specific number of creatures (including single-target spells such as disintegrate)】，但射线这类“类武器法术”算不算“指定特定数量目标”的法术一直有人吵。附议
这句话里面举的例子是解离术，但解离术除了是射线以外，还有自身“只影响第一个目标”的限制，我觉得在此并不是以其作为射线的代表而受制约。
而从常识来说，电爪长剑不能生效，而电击长剑能，闪电箭不能而闪电瓶能，也都太诡异了。表现相同而效果完全不同，也显得太抠了。
我会倾向于认为所有接触和远程接触类不受这句制约，因为它们并不是“目标为特定数目生物”的法术。
James Jacobs 早年有个回答 (https://paizo.com/community/blog/v5748dyo5lbjm?Get-Lost#8)也这么讲。