User blog comment:Krayfish/Hypothetical biochemistries/@comment-796766-20120923154502

In response to Holben's point on the RoC, I must say that it need not be just awesome. The narrative gain from the concept is also taken into account. For consistency, I'll define 'narrative gain' as 'the amount of positive contribution to an arc, be it narrative or character in nature, by any tool such as a concept, character, or conflict'. Certain alternate biochemistries could, in fact, offer enough narrative gain to be protected by the Rule of Cool. Examplis gratis, a germanium lifeform would likely be metallic in nature; Imagine such a creature joining GSSOC. How would they react to the food, the weapons, the pathogens in the air? Wouldn't they require a practical and personal life support system, like the quarians or volus from the Mass Effect franchise, or the humans on Pandora from Avatar? What would happen if such a system were compromised or damaged in battle? Perhaps they could suffer an allergic reaction from certain carbon-based pathogens, making a common cold into a deadly allergy.

In summary, while a number of ABs (alternate biochemistry takes too long to type this much) would prove of little narrative gain and thus be unprotected by the RoC, a few such as germanium or silicon would prove to be both plausible enough and of enough narrative gain to be within the limits of the Rule of Cool.

At the same time, however, species with ABs should be very alien in appearance. A silicon-based species should likely appear crystalline, and have very different approaches to life functions; Feeding on electromagnetic radiation, for example, and communicating by way of harmonic resonance (that is, by vibrating in certain pitches with each other). Germanium based lifeforms would likely appear very metallic, and would be more likely to feed on the chemical energy found in minerals from stones (meaning germanium herbivores would likely be eating rocks). This means that the Avetza would need a massive appearence retcon if they're going to remain silicon-based.

So the official REST vote and verdict on alternate biochemistry is:

Limited REST Approval