A deadly swarm?

[Asmo]

Contains spoilers for "Tomb of Chaos"!!
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A room in the temple contains a hoard of coins that will turn into a bat swarm with construct traits after one round if touched.
Bat swarm + construct traits; what will damage the swarm beside fire damage ( oil, torches, alchemist fire, Burning Hands and similar spells)?
Will Magic Missile work? Melf´s Acid Arrow? The party is lvl 3 and got 2 clerics, one wizard, a scout and a fighter. They are pretty maxed out, but I guess that this will make them confused. They have no special weapons that works against swarms.

Asmo

 

[Ilium]

Magic missile (and acid arrow) will not work because swarms are immune to targeted spells. These things will be nasty against a 3rd-level party. Will they have the ability to flee?

 

[Pinotage]

what will damage the swarm beside fire damage ( oil, torches, alchemist fire, Burning Hands and similar spells)?
Will Magic Missile work? Melf´s Acid Arrow? The party is lvl 3 and got 2 clerics, one wizard, a scout and a fighter. They are pretty maxed out, but I guess that this will make them confused. They have no special weapons that works against swarms.
Asmo

Swarms are always tricky - at that level fire certainly works best. Fighters hitting them with torches, rogues throwing oil or alchemist's fire, etc. Flasks of acid work as well or generally any area effect (since they take 50% extra damage from area effects). It only has 13 hp, so shouldn't be too difficult.

Pinotage

 

[Ilium]

Are you planning to give it the extra Construct hit points based on the size of the swarm as a whole? If so, and if the swarm is Large, it will have something like 35 hit points instead.

If you base it on the individual creature's size, then it gets only 1d10 with no con modifier, so it would be 10 at most. I don't know how which option a construct swarm should use. I think MM III has one, but I don't have my books here.

 

[Asmo]

I will adjust its hitpoints to 18, we´ll see if its´to much. I hope the party has a sense of self-preservation and knows when it´s time to run if things gets out of control

Asmo