Hmmm... that's a classic equivalent to that in fantasy worlds: Dragons. You may want to check Witchaven's dragon, you can see it on the first level of the Witchaven shareware version (the first one) - at least I remeber playing the demo when it was released and found the dragon in the early beginning, which surprised me positively since I would only expect monsters such as those in the last maps, with impossible difficulty.
I dont know to which extent the fantasy will prevail over a more realistic view in TSP, the project that has a scope big enough to contain any idea, so I'm not sure if dragons will make it to our mods... They are sure hard as hell to draw, they are big and have loooong bodies, which makes the fact they are flat sprites that much more obvious - again, just take a look at Witchaven's dragon and see what I mean...