Well, we could've just had dragons running around like wolves, but I thought a little more diversity might be nice. So I plucked out my copies of "The Future is Wild" and "After Man: A Zoology of the Future" and chose a couple of entries of some people's vision of how life will continue after all sapient beings are removed. And then made them
dwarfy.
In this case, the premise would be that some strange burst of energy from the sky shortly after the creation of the mortal races wreaked havoc on the genes and reproductive systems of all animal life, causing catastrophic damage and the collapse of civilization. However, water diffused the energy, so that things in water could escape with just mutation, and things both underground
and underwater (or underground and in magma) escaped without alteration. The only original land animals that survived were tough scavengers (or very fast breeders) with strong resistances to toxins and disease, and even they were...
changed. With biomes like these, who needs evil?
Rabbucks - Descendants of the common rabbit, their rapid breeding has enabled them to diversify and grow strong. They could be domesticated, bred, and used as pack animals or wagon-pullers. The last dwarves--last civilized beings--in the world will use a pair of them to move the wagon filled with what little they could scavenge from the Mountainhomes to a place with a new beginning.
Wily Coyotes - (Sorry) Rather like wolves, they are more adaptable to variant environments but a bit scrawnier.
Rotgut Vultures - Descendants of the vulture, gorged on the flesh of countless dying beings, these have gotten as big as the giant eagles of old--but these live everywhere.
Toraton - Turtles were not sterilized by the strange rays of the sun the way most land animals were--they were changed. Taller than elephants, and of unceasing hunger, they gather wherever there is fresh water to drink or vegetation to munch.
Flish - Fish have learned to fly as well as swim, to evade the other things beneath the surface. Modeled after their pike ancestors, these too have learned to dwell wherever there is water.
Megasquid - Chief rival in vegetable consumption to the Toratons are these. Squids which have been altered and reach absolutely incredible size (larger than Toratons or Dragons of old), these creatures actually eat less than their size would denote, due to their metabolisms--which just means many more of them can travel together. They'll eat anything, not just vegetation: go ahead, try and stop them.
Squibbon - A smaller, smarter relative of the megasquid, these descendants of the squids are on their way to becoming the next primates. Perhaps, in the distant future, the descendants of these beings will be the ones to carve mighty fortresses. For now, they'll hit you as hard as a gorilla, with as many arms as the naughtiest of the HFS, while stealing your stuff like the rhesus macaques.
Swampus - A sadistic distant relative of the squibbon, it doesn't want your stuff. It wants to lurk near the water, hidden from sight, flay the skin from your back and inject debilitating venom into you, giving it time to chow down on your quivering carcass.
Lurkfish - The carp did not pass from this world. But they were taught a very special trick by the eldest of beings, and while they are kind enough to remain in the water, that will be of little help if you insist on going toe-to-toe with them--or keeping your booze stockpile near the river.
Ocean Phantom - Remember the sea monsters? You can be forgiven if you didn't: there weren't many of them and they stuck to evil biomes. These venture beyond, breed more, and along with everything else they do to you, they'll suck your blood in the process.
Carakillers - They're like turkeys. Large, evil-tempered, flightless turkeys who hunt in huge packs and will kill you and everything you love. Good eating.
Desert Shark - Not actually descended from great white sharks--probably. They hide in rivers or deserts, and they show no mercy.
Wagons
Dwarves
Humans
Elves
Goblins
Kobolds
Dragons
HFS
Purring Maggots
Cave Lobsters
Cave Crocodiles
Giant Toads
Giant Olms
Fire Imps
Giant Cave Spiders
Cave Spiders
Cave Fish
Fire Snakes
Olms
Fire Men
Magma Men
Olm Men
Obviously, not all of these will actually show up on the same fortress for a succession game, but I got a little carried away with adding more horrible things to kill you (I might make it into a stand-alone mod eventually, and I definitely will in the next version). I've genned a large world with these, gotten the Age of Death satisfactorily, and found a site with magma, flux, forest, river, underground river, underground pool, a chasm, and HFS. It's a large embark, 8x8, but the very low number of dwarves will keep the FPS down for quite a long time...