Swarmfighting Monster?

[Seclora]

So I'm trying to figure out a monster specifically able to combat Swarms. The particular swarm we've been dealing with is a homebrew combination of the Moon Rat from MM2 and the Cranium Rat Swarm(Psionic Variant) from the Fiend Folio, if it matters.

I'm fairly open to any suggestions, and the setting is fairly permissive of Rules exploits (Cleric is running DMM: Persist, we're burning multiple Miracles a day, and we're building a steam-powered motorcycle using Prestidigitation).

What do y'all suggest?

[kardar233]

Things with powerful AoE effects are good. I'd go for a dragon of some kind; you should be able to get a Hellfire Wyrm (MM2) with Gate as it's native to the lower planes.

[Seclora]

Dragons are all dead, sadly, although we are working on that.

And they've been using their Psion manifesting to get resistance and immunity to elemental damage.