What is Eight Palaces?

A classification system that assigns each of the 64 hexagrams to one of eight palaces (☰ Qian, ☷ Kun, ☳ Zhen, ☴ Xun, ☵ Kan, ☲ Li, ☶ Gen, ☱ Dui). The palace determines the hexagram's ruling element, which serves as the reference point for calculating the Six Relatives of each line. The Eight Palace system was codified in the Bushi Zhengzong.

Source: Jingshi Yizhuan (京氏易傳), Jing Fang; Bushi Zhengzong (卜筮正宗), Wang Hongxu