Arioch wrote:I suppose it's possible for organisms to derive energy from the temperature gradient generated by the decay of radioactive elements, but the density of such material would have to be much greater than I think you're likely to find on the surface of a conventional planet. Radioactive elements tend to be short-lived and rare in a planet's crust. Having this material dense and pure enough and of only certain isotopes to allow for a fissile chain reaction (such as happens in a nuclear reactor) seems virtually impossible in a naturally-occurring environment, even if we're talking about exotic planets such as might form around a supernova remnant which might have a plentiful supply of such heavy and and unstable elements. it's quite difficult to artificially enrich U-235 to the point where it can sustain a fission reaction; it's hard to imagine this process occurring naturally.
There are bacteria that derive energy from radiation on Earth. But as I recall they have very slow metabolism. Faster, intelligence supporting metabolism would depend on concentration of radioactive material through some mechanism. Perhaps a food chain rooted in slow growing bacteria or plant-like life might provide such a mechanism. This would be similar to how Humans depend ultimately on plants for sustenance, either eating them directly or after the energy has been concentrated by herbivores.
I'll include URL's to a couple of articles regarding radiation consuming bacteria on Earth:
https://www.sciencedaily.com/releases/2 ... 192814.htm
https://www.newscientist.com/article/mg ... ste-safer/
Lets give these hypothetical intelligent radiation metabolizing critters a name, Nucleons will do as a placeholder name.
Nucleons might be at the top of a whole food chain of other radiation metabolizing creatures, with radioactive material being concentrated at each step in the chain. At the bottom are perhaps slow growing single cell organisms similar in role to the radiation dependent bacteria that exist on Earth. The next step might be some sort of sessile filter feeders that consume the bacteria. Next would be "herbivores", mobile animals that eat the filter feeders. Then "carnivores" that eat the "herbivores". Then, at the top of the food chain, nucleons, with enough radioactive material concentrated in their tissues that they can move and think at a rate comparable to the carbon/oxygen/water life we are familiar with.
Furthermore, Nucleons don't have to be from common barren planets. Perhaps they come from a unique planet, a supernova remnant as you suggested. That would seem to require a unique star, a white dwarf or better yet neutron star. Perhaps there is a whole category of planets associated with such stars, call them radioactive planets. These would have the atmospheres blown away. The basic type would combine a radioactive climate zone with an airless climate zone. Alternately, there might be radioactive iceballs, with radioactive zones, vents, and airless. The distinction between radioactive and airless is clear: the half sphere that faced the star when it exploded is radioactive, the other half is merely airless. Perhaps the only planets of these types are in the Nucleon home system.
Blue giant stars might have planets with radiation zones, the description even mentions radiation. Though I expect the description mostly means solar radiation, not radioactives in the crust like nucleons would want. Perhaps there are uncommon but not unique radioactive planets scattered around the galaxy, that can orbit any star, products of random concentration of supernova debris in population I stars. Here's an article describing the difference between population I and II stars:
https://www.britannica.com/science/Population-I
Maybe the game could consider radiation an extra attribute like temperature and atmosphere. If present the planet is hostile or infertile to most races, but not to Nucleons, probably not to Wrenn, and maybe not to the hardy Yoral. Orthin can surely ignore surface radiation, but perhaps not inherent radiation emanating from a radioactive core.
Once they evolved intelligence and learned to create technology, Nucleons would not be dependent on the complex food chain that evolved on their home planet. They could use technology based mining and enrichment techniques to create radioactivity-dense feedstocks, adding flavor and micronutrients by feeding this technologically derived "cattle feed" to an appropriate "herbivore" from their home planet, perhaps genetically engineered. Thus my stipulation that they don't eat food, but consume metal, possibly indirectly, for sustenance.
I would suggest Nucleons get a racial mining bonus so they don't fall too far behind the other races in the quest for metal due to consuming a large fraction of their metal production for sustenance. Perhaps they get +1 or even +2 metal from every mine. And any barren world (not iceball) that has a radioactive zone is treated as mineral rich for nucleons, including their home planet.
Nucleons probably would not start with the ability to build farms, which are useless to them. A technology would be added to their tech tree that allows them to build farms when mastered. Other races all have this tech at start: agriculture. Dismantling captured farms could give reverse engineering credit to researching agriculture. They do need to eventually master farming so they can feed conquered populations.
Sorry for the long winded post. I suffer from manic-depressive disorder, and weirdness like this results from the manic phase.