Infested creature template

[Rust]

A couple of years ago I remember finding in one of the 3.5 source books various templates including one for something along the lines of an infested template. I toyed with the idea of using it with a gargantuan golem that during it's millennia of inactivity had become home to a swarm of rats.

I still love the idea but unfortunately I can't remember where I saw it. Can anybody point me in the right direction?

[The Viscount]

Were you perhaps thinking of the Hivenest template from Dungeonscape? It's a template that puts a swarm in an undead, plant, or construct.

[ShurikVch]

Unfortunately, Hivenest is specify a swarm of vermins. Rats can be a pests, but not a vermins in D&D terms.

Probably, Symbiotic Creature from Savage Species can fit the bill? Golem as host and rat swarm as guest?