Thanks, Footkerchief!
After reading some of this stuff, I feel that the more DF progresses, the more it would turn into a torture game, as opposed to the RTL game it was meant to be.
The Sims doesn't have any flaying mechanics at all, and look how sadistic people became there.
I distinctly remember somebody... somebody who couldn't possibly be me, I swear... locking children who got bad grades in a room with an unguarded fireplace and thousands of wooden easels. Oh boy did they run around like a digital chicken with its header file cut off.
Imagine what happens when people who play DF and not The Sims get their hands on
the ability to flay muscle from the bone. I have a feeling I'm going to end up training hundreds of dwarves in toughness (which could be harder with the new skills system, unless it makes pumping give toughness and strength more often than before for example) and then crippling them in horrific ways. I intend to conduct an experiment - purely for scientific research, you understand - on the relative crippling potential of the different attack types. While a compound fracture could be pretty bad, who's to say that 'ringbarking' would be any better?
You'd have to have some pretty bizarre biology to get diatomic hydrogen gas, though.
I figured helium would be even less likely (unless they replenished it as a food source from radioactive locations?), and that pretty much covered the off-the-top-of-my-head lighter than air gases. Wikipedia suggests ammonia and methane. Methane could be obtained by eating (or collecting the gaseous emissions of
) ruminants (cows, etc.) or harvesting it from decomposing organic matter. For ammonia, it could come from decomposing organic matter and some legumes, though it seems (biologists please correct me) it could be converted into ammonia from some ammonium compounds and so could plausibly be used.
So I guess it comes down to plausibility or having giant spiders with flaming sacks of silk fall from the sky under certain conditions. Methane has an auto-ignition point of 580 degrees Celcius (11044 degrees DFT), which is unlikely unless close to magma. Fortunately the flash point is -188 degrees Celcius (9662 degrees DFT), so it will catch fire in the presence of a flame unless your dwarves are dying on their own anyway.
Then I mod in another caste with a fire-based attack, and presto, we have a set of flying kamikaze ninja spiders supported by fire-powered officers.