Staunchmoss

Staunchmoss is a stringy gray moss that forms at the very tops of the oldest coniferous trees.  It has a spongy texture and a structure not unlike wool, though with much thicker strands.  It grows only during very cold weather, and rapidly deteriorates when above freezing when not preserved properly.  While fresh or preserved, Staunchmoss has nearly magical curative properties.  Staunchmoss will stop all but the most grievous of bleeding wounds, and can neutralize minor poisons and infections.  When in the hands of a trained surgeon, it is even possible for recently severed limbs to be reattached and eventually be fully functional again.

Harvest

The process for gathering and cultivating Staunchmoss is difficult, and given its specific habitat and climate requirements, it only grows in ancient pine forest areas near the poles.  The trees must be at least 60 feet tall, requiring hundreds of years of good growing seasons without substantial storms or forest fires.  Even then, the moss will only grow in winter and the harvest and preservation techniques are often kept secret by the families, villages and trade companies that have devised the proper techniques over generations.
First, when the moss has grown to maturity, it must be very carefully cut away from the bark to prevent premature deterioration.  Some harvesters choose to scrape the very outermost section of tree bark along with the moss, but then measures must be taken to preserve the health of the tree.  The moss will save for up to two weeks this was so long as the weather stays cold.  Before the spring thaw, the moss must be preserved by being brined cold in strong alcohol, then salted and dried completely.  After the alcohol soak, the moss will tolerate slightly warmer temperatures, but still must be kept cold while it dries.  After that, the moss can be used at any temperature, so long as it remains dry.
When used, the moss will dissolve shortly after contact with blood, cauterizing and purifying the wound.  With proper applications by someone with masterful medical knowledge, it can greatly aid in otherwise impossible procedures.
On its own, bloodmoss will heal 1d8+4 hp and allow for one save against an ongoing poison or disease effect with a +2 item bonus.  Combined with a Medicine check, it will give the item bonus to both the medicine check and any applicable save, it will turn a critical failure into a regular failure, and it will add an additional die to any healed hp.