Those underground areas honestly reminded me most of those old maps of 2d forts... but for the stairs symbols all over the place.
I wonder how much protection the common villager has against these things? I mean, if your root cellar just has an open hallway leading into the catacombs, where vampires are coming up to feast on human blood... what, exactly is stopping them from rampaging out through your house, and then on to the streets?
Those maps look very easy to get lost in... we're going to need more breadcrumbs. (Or should I just snap off ratman parts to mark my path?)
Speaking of which, while undead are obviously getting a lot of love, I hope we can see some ratman or sewer alligatorman or something tribes down in the muck, as well.
Stumbling across a band of friendly molemen down in the lower reaches, before the catacombs give way to the caverns proper would make for a cool staging area for further exploration.
For the most part it isn't that tough for people to survive.
Generation goes WAAAY out of its way to ensure that megabeasts and semimegabeasts live. I mean if a hydra attacked your town would you solo it or get the entire town watch on it? It also goes out of its way to make Megabeasts and Semimegabeasts oddly harmless... Rampages feel more like Sunday Brunch and I would have no problem with less frequent megabeast attacks but with a lot more damage.
A group of 5 soldiers can dogpile and kill megabeasts in adventure mode (disapointingly)
For the most part though as powerful as a creature is, an army is a good deterrant.
If anything I'd like to know how different races could actually, reasonably, die.
I find that elves and humans reliably survive, but goblins tend to get chopped to kibble just because they're at war with everyone else, and dwarves tend to starve to death an awful lot, or have populations low enough that night critters are capable of keeping pace with dwarven reproduction rates. Kobolds often go extinct, as well.