Legend & Origin
The root of the Tai Sui belief is, of all things, astronomy. The ancients observed that Jupiter — the 'Year Star' — circles the celestial sphere roughly every twelve years, so they divided the sky into twelve zones; each year Jupiter passed through one, and that zone had its own Tai Sui spirit on watch. Over time this grew into the full system of sixty Tai Sui in rotation, each with his own name and rank.
Folklore adds a story to make your skin crawl. Long ago, someone who scoffed at the taboo deliberately dug into the ground in the Tai Sui's direction — and unearthed a lump of flesh that kept growing and could not be cut through no matter what. Terrified, he hastily reburied it and set up an altar to it, and from then on the warning spread: never break ground on Tai Sui's head.
The curious part is that the 'Tai Sui fungus' in the tale really does exist — an underground fungus shaped like a mass of flesh, exactly the kind of thing that would unnerve the ancients. One belief, with one end tied to the stars and the other to a mystery buried in the soil: Tai Sui may be the most cross-disciplinary god of them all.