You rang?
Nitpick: "wherefore" actually means "for what reason", not "at what location".
I like it. I don't use the taint system much but I'd definitely give a tainted minion some of this stuff if I sent one at my players.
I'd definitely be down for a Redwall- or Mouse Guard-themed game. For those not familiar with the latter, it's a comic series that's sort of the gritty realistic version of Redwall (well, realistic other than the talking mice with swords). Also in Mouse Guard only the mice have humanlike intelligences and the relative sizes of the animals is taken into account more consistently.
Also, time for a contribution! It's not really a special material in its own right as it is a means of producing a special material, but that's close enough.
Virus Ink
This foul greenish-black liquid is produced by distilling a number of alchemical reagents with ichor drawn from plague victims' sores. Extracting the necessary fluids takes one minute and deals 2 points of Constitution damage to the source creature (which must be a humanoid suffering from any nonmagical disease which damages one or more physical ability scores). In addition, the source creature must immediately make a Fortitude save at the same DC as that of the disease from which they are suffering. If they fail, they are also affected as if they had failed two of the normal Fortitude saves forced by the disease (for example, a victim of filth fever would take an additional 2d3 Dexterity and Constitution damage). A vial of ichor is successfully collected even if the source creature dies in the process, and the rate at which ichor may be extracted is limited only by the source creature's resilience. After the ichor has been collected, it must be mixed with a number of common alchemical materials costing a total of 10 gp per vial of ichor to be processed. Each vial of ichor (and its accompanying reagents and catalysts) produces one dose of Virus Ink.
After the ink has been prepared, it must then be etched into a living creature's skin (or the skin of a corporeal, fleshy undead such as a zombie or vampire) in the form of a tattoo, which takes 10 minutes and requires reusable needles and tools costing 15 gp. This process is extremely painful; the creature receiving the tattoo takes 1 point of damage every minute while the tattoo is being applied, and if they attempt to take any action other than writhe in agony they must first make a DC 25 Fortitude save. If they succeed, they may take a single move or standard action (usually moving away from or attacking the creature applying the tattoo); if they fail, they are unable to act that round. The tattoo can still be successfully applied if the recipient dies during its application, but Virus Ink tattoos exhibit no special qualities (and fade after only a few days) unless the recipient was alive when the procedure was started.
A creature with a Virus Ink tattoo is immune to the disease possessed by the source creature of the ichor used to produce the Virus Ink, and targets struck by the tattooed creature's unarmed or natural attacks must make a Fortitude save at the disease's normal DC or contract the disease themselves. In addition, a struck creature which already had the disease must make a Fortitude save at the disease's normal DC or suffer the effects of a normal failed save against the disease.
The tattoo retains its properties even after the tattooed creature's death, and armor or clothing crafted from hides marked with Virus Ink tattoos confer the benefits of the tattoos to its wearer.