Herbs that had grown for three hundred years took time to soften. Their fibers held minerals drawn out of the rock. Three degrees too hot would burn the Frost-Lotus. Four too cold would leave the Iron-Root Vine in a lump at the bottom. Pei Jing meant to hold the fire at four hundred and twenty degrees for three days.
Day One began at the sixth morning bell. He opened two carboys and poured ten gallons of dragon blood into the bronze cauldron. It struck the hot bottom with a hiss. Dark foam rose with a metallic smell.
He added Earth-Core Fungus and Iron-Root Vine. The fungus sank. The vine curled against the wall like a length of wire. Pei Jing fed two currents of Gang Qi into the cauldron and made them turn against one another. The broth moved gently enough to carry heat through both herbs.
Every two hours he skimmed off the gray fibers that rose to the surface. By midnight the vine had dissolved. The dark red broth turned ochre and thickened like pitch. It smelled of wet soil and iron ore. At the bottom of the vessel, the hearth gauge still read four hundred and twenty degrees Celsius. Inside the pot the broth was much cooler. It held a slow simmer.
