[Varyon]

Originally Posted by sir_pudding

Boiled linseed oil has antibacterial and and antifungal properties and is a pretty traditional sword oil

Awesome.

Originally Posted by Anthony

If the shapeshifters form pockets like this naturally, they probably have a biological means of keeping them clean that gradually pushes contaminants out

"Naturally" doesn't really apply, as they are basically a race created by magical experimentation that mashed together aspects from various species (some of which have supernatural qualities themselves). The Feuyaner are simply able to reshape their bodies in a variety of ways. Flesh pockets aren't one of the "preprogrammed" options (unlike the reflex-style armor they can grow), but are simple and handy enough that most opt to grow them.

Despite the magic in their origins, I don't want a magic-based solution - most Feuyaner aren't mages, and permanent magic items in the setting are addictive if one is overly exposed to them (and keeping a Gem of Minty Freshness in one's flesh pocket all the time would certainly qualify).

Originally Posted by Bruno

The key factor is that they're not wet. A flesh pouch, such as a marsupium (the marsupial pouch) is not a mucus-membrane lined cavity, like the mouth or various other body parts I won't mention. There's no pools of saliva, mucus, food debris, or body waste, just skin. The baby is a bit messy, but the saliva from washing does dry up pretty promptly, after which the pouch can be kept more carefully closed when necessary. I don't know about you, but my various sphincters are pretty darn good at keeping things out of my mouth when I want them to, and letting air into or out of my mouth when I want them to.

The material lining the pouch is simply thick, leathery skin (without sweat glands, fortunately), and it has a decent but not perfect seal. I had assumed incidental moisture - sweat dripping in from elsewhere on the body, rain, etc - wouldn't come out on its own, which would result in such pouches often having some degree of dampness to them. Considering cheek and marsupial pouches, however, implies you're likely right that this is unlikely to be an issue.

The "flesh sheath" for the sword is more problematic, as that is likely to get biological fluids like blood in it, but I intend the character to not make heavy use of that (it's a backup weapon), and to do his best to give it a thorough cleaning anytime he does spill blood with it.