The Golden Saber Rice is a special grain found in the Holy Realm, and it contains a sliver of earth essence. Not only would it enhance one's cultivation after consumption, but it would also enhance one's physique.
The Golden Saber Rice is just like any other spirit herb. It's decided by age and quality, with no distinction between grades. Furthermore, the further the age, the more limited the rate of growth would be, which is why most people wouldn't go out of their way to cultivate it.