The Ten Heavenly Stems (Tian Gan)

Ten portraits of qi

This is the longest and most quoted chapter: a character portrait of each of the ten stems, described by what it can and cannot do. Jia (yang wood) is a towering tree that needs fire to hatch and dislikes metal in spring; Yi (yin wood) is a vine that will cling to Jia to survive any season. The portraits answer one practical question for each stem — what does this element need, and what breaks it?

Read them as a key for the day master: a Bing (yang fire) day master is fierce and melts metal, but wilts against Xin (yin metal); a Gui (yin water) day master is the weakest branch of water yet works its greatest transformation when it combines with Wu (yang earth). The chapter is best used as a checklist of strengths, not of fates.