Khav (also kha-khav) is a perennial herb about half a bu tall, with a very straight woody stem slightly squarish in cross-section. It has many branches protected by dense hooked spines, narrow oval leaves, and in season, threefold clusters of light green flowers that turn almost pure white when dried. Its fruit is a dry capsule that looks like a nut, but with a lid that pops open when it falls to the ground, releasing a dozen or so seeds.
Khav grows only in the northern areas of the empire, and prefers dry salty soil at moderately high altitude.
Khav's sole medicinal value is in its roots, which are one of the most yang-dominant ingredients available to the herbalist. Taken by itself, the powdered root sharply increases the circulation of blood in the head, torso, and thighs. This allows the person to sustain consciousness in circumstances which ordinarily would result in unconsciousness. However, when unconsciousness does eventually prevail, the liver and spleen quickly filter khav from their meridians, quickly counteracting its effects.
The highly imbalanced nature of khav limits its usefulness in more complex formulas, as without a strong yin counterweight the khav's energy can easily overwhelm any more subtle qualities that the herbalist may be seeking. Master herbalists can with care neutralize the yang of khav with a powerful yin component such as millettia or jixueteng, but the balance is extraordinarily sensitive, so measurement must be very careful and the herbalist must consider thoroughly all the interactions arising from every ingredient.