Thanatos is an ice-ocean planet, like those damn moons you hear about
all the time. Tectonic movement and tidal forces warm up the insides,
and the ice is melted at the surface. It's water, nothing fancy.
Noxians are giant, trisymmetrical snake-like creatures that
communicate with light, and have clawed tentacles sprouting from under
the protective beaks. The beaks also have three eyes mounted in them.
The noxians evolved from tripartite creatures, but they do learn to
swim a certain way, and thus acquire a developmental bipartite
symmetry: that is, for example, one "beak-thingie" becomes "below",
and the two others become the top. Possibly one or the other of these
configurations become stratified and ummovable, and so forth and so
forth.
Noxians have a very old and very slow culture, because they are
ridiculously long-lived themselves - or rather, they are naturally
cryogenic. They often go into hibernation, and can wake up ten years,
tens of years later.
They could, and can, survive in the cold waters beneath the Arctic
ice.
--
Kristian Järventaus