Rat cave

C rat cave
See Cost	2

Rat caves are two levels deep and packed with sewer rats. If you leave immediately upon entering one, you'll still probably have to beat off three or four rats that follow you up, so they're probably the biggest reason not to explore caves in the early going.

If you want to clear one out, you'd best be extremely good against swarms. The first level typically channels its inhabitants along a 2-4 tile wide path to your position on the upslope, so you'll typically not have too much trouble with being surrounded. Likewise, they don't hold back: once they stop coming, that floor's pretty much done.

The second level is the home of the elusive rat king. It'll infect you with ratting disease probably as soon as you can see them, but apart from that the King is less dangerous than its troops: there's a smaller swarm of rats to attack you directly. (As of 02Feb, you'll need to stay there long enough to vomit, repeatedly, before there's any effect on your genes or you start mutating. The Rat King is not a significant source of mutations.) Go easy on the area-effect weapons though, as Rat King lairs typically have high-tech loot.

For the record, the Rat King has no special reaction to Rat-mutated characters.