Has it occurred to you just how many cavern creatures in Dwarf Fortress are just underground-living variants of surface creatures? Here's a mostly-complete list:
Listed by the shallowest cavern layer it is found in.
Cavern Layer 1:
Bats, Giant bats*
Blind cave bears
Cave crocodiles
Cave fish
Cave lobsters
Cave spiders, Giant cave spiders
Cave swallows, Giant cave swallows
Giant earthworms
Giant moles
Giant rats, Large rats, Rats?
Giant toads
Helmet snakes
Naked mold dogs*
Olms, Giant olms*
Cavern Layer 2:
Blind cave ogres
Cavern Layer 3:
Cave dragons
*Okay, these creatures or their closest counterparts often live underground IRL, but little caves and tunnels and stuff aren't really implemented so the cavern versions aren't really the same as the RL versions.
Note that this list does not mention subterranean animalmen,
creatures with multiple component creatures, creatures with uncertain but probable surface origins (such as voracious cave crawlers and
Two things I noticed about most of these critters:
1. They were mostly found in cavern layers 1 and 2.
2. Most are just "Cave X" or "Giant X" or something like that.
This probably makes it all the easier to make new cave beasties from scratch.
Here's the gist of my idea:
Many of the aforementioned beasts would be removed from the raws. Some favorites, like the GCS, helmet snake, and giant toad, should be left in alongside blind cave ogres and cave dragons (which have different depths than the rest, which matters--see below), and the non-cave-animal creatures. Some of the subterranean animalfolk would also need to be removed.
To replace them, a new system would come into play to make new cavern creatures. Creatures from biomes near caves, plus some from anywhere, would be randomly selected and copied into new files, sorta like how titans and forgotten beasts are put into files. The creatures would be given a new CREATURE: name, as well as getting a bunch of changes, which should and/or could include:
Should:
-Changes to the name, such as "cave X," "blind X," "blind cave X," "giant X," etc. Perhaps some new ones, like "deep X" or "underground X" could be added.
-Changes to pigmentation, typically making skin/hair/etc paler and eyes red.
-Changing the description to try to accommodate the new appearance and such. This would be the hardest part--perhaps it would be better to just write a new description, e.g, "A massive toad which has adapted to the lightless depths. It has pale green skin and red eyes." Or something like that.
Could (on an individual-creature basis):
-Remove eyes
-Stunt/remove wings, or other body parts. This would remove the ability to fly or grasp or whatever, depending on the stunted part.
-Increase size
-Possibly, decrease size (e.g, "Pygmy Cave Elephant"...now I need to go mod).
Some more ideas based on research by Silverionmox:
-Antennae, or adding/increasing other nonvisual senses (smell, hearing, infrared sensing, etc); some of this might be hard to implement until EXTRAVISION gets broken up.
-Vestigial body parts
-Higher SPEED, to conserve energy
-More interested in exploring
More ideas could be included.
The benefits of this idea include:
-More variety in cavern life
-Easier implementation of modded wildlife into DF's caverns
-Possibly, more Fun. Cavern layer 1 is often described as usually less dangerous than the surface, because the risks of hidden thieves or ambushes outweigh the occasional GCS or troll. Random animals could shake this up. Elephants were terrifying on the surface; imagine what they'd be like underground and blind! Well, about the same, except you can't see them.
-More mystery in the early caverns. Currently, caverns are just another place to settle, except that (since every fort has caverns under it) everyone knows the ins and outs of it. Again, adding random cave critters could easily make things more interesting.
-More interesting caravan choices and goblin mounts. The dwarven caravan is currently treated as little more than a way to easily get steel. Imagine if they brought deep bears and giant cave carp! The same goes for goblin mounts, except that goblins mounted on oversized, pale fish doesn't sound very intimidating.
-Verisimilitude. This way, most animals which live in the caverns could have gotten there, and any kind of animal can live there. This goes double in the case of low-fantasy creatures like unicorns and beak dogs; if giant, predatory mole rats and blind bears can live in caverns, why can't horses with horns and two-legged pack predators and such live there, too?
Summary: I propose that a system be implemented to allow random creatures to be added to the caverns, similar to current "Cave X" and similar creatures. This will mainly serve to add variety in its various forms, but will have other side benefits as well.