From the Introduction:
There is power in the fruits of nature. And in the seeds, stems, roots, and leaves, too. In worlds with sapient animals, some animals have discovered that particular combinations of plant components, called herbs, can influence others' minds, speed the healing process, or even harm enemies if properly mixed and applied. Sometimes called "natural alchemy," this primitive chemistry is often mistaken for magic by observers. And some herbalists guard their secrets as closely as any mage, lending a further air of mystery to their craft.
Any animal with levels in Herbalist lore can try to concoct or deploy herbal mixtures, but only those with Herbalist as their niche can ever truly master the craft. Masters of herbalism often serve as advisors to pack leaders, beast kings, and other rulers of animal communities. Their potions and powders are useful for the control, and sometimes elimination, of rivals.