Nerethae aka the Hardyherb

Nerethae, often colloquially called the Hardyherb, is a plant only met in The Last Barrier. It's historically only been found in the Nival to upper Alpine levels on the central mountain range, but since the creation of the Auterhenatirini ice sheet the species has, through unknown means, appeared on the central to northernmost parts of The Cold Wastes as well. The Hardyherb seems to be one of the few plants that thrive in the Wastes, to the degree that the variant found there grows larger and has more potent effects than the original, mountain-residing variant.
Despite the herb preferring such harsh and remote area, it was discovered only a century after our Arrival to the Last Barrier. Of course it was a deredel who discovered the plant, naming it Stoneroot originally due to the rocky ridge where Ze found the plant. Ze took one specimen with them to show it to others and even tried to grow the humble-looking plant, but it soon died, unstudied, and the plant was mostly forgotten for a long time.
In fact, the medicinal properties of the Nerethae plant were only found a few centuries later. It was found that the herb could be used as a more efficient substitute to several herbs to treat a variety of illnesses, and even as a only functional treatment to Cold Rot. These discoveries raised the price of the herb drastically practically overnight, as all healers wanted to have a stock of the herb. This was, of course, aided by the fact that to this day, no way to cultivate it has been found. The Hardyherb is notoriously picky where it prefers to grow, and any tries to introduce it to any other environments have been unsuccessful. As such, an entirely new profession has risen to supply these vital herbs (along with others) to those who need them.