Sanitalere

Other than the Otonomoi ability to see better in the dark, the other benefit that Humans derived from us, and still do in great amounts, is our greater ability to sustain damage and then be brought back to full function after the fact.
We are not invulnerable, of course, and the removal of an arm or eye is just as debilitating (as well as equally painful) as it is for humans. Thankfully, ours can be brought back far more easily than theirs. A simple material makes such medical magic far easier. Well, 'simple' may be far too subtle a statement for what Sanitalere is and does.
A Glasscutter of either variety can repair most any wound that has not outright killed the Otonomoi who bears it. It takes time, with Human glasscutters able to be substantially faster than Otonomoi but still not anywhere near instant. Not to mention that the repair will have to be monitored continuously to ensure that the replacement limb will not grow into some malformed horror and necessitate cutting off the limb a second time.
The panacea to those problems is Sanitalere. By applying the prepared version of that stone, the process is vastly shortened and the worst of the process can be circumvented almost completely. In near an instant wounds will close, sickness will be purged, and the the Otoi being administered to will be invigorated, even if their wounds are not completely healed. Even if they are not totally revived, there seems to be little downside to simply applying more Sanitalere bar the material's rarity.
Similar in composition to a strange mix of marble and ceramic, the stone can be found in a variety of places but none of them are places someone would like to frequent, namely the Silent Cities. It has, on occasion, been found like true stone, which is to say buried within the earth, but the most common form is as a...growth upon the usually uniform and simple shapes of the buildings that make up the Silent Cities. Growth is the most appropriate term as well, as Delvers who go searching for Sanitalere will often leave smaller nodules of the material in place so that they can return later to harvest more of the material.

Type

Biomaterial