Chapter 2: Holy Beast (ZODIAC)
The ancestors of the 12 most numerous species of animals are called holy beasts. They have intelligence and many magical power, they only breathe air and eat plants to live.
The 12 ancestors realized that the more intelligent descendants they have, the stronger they will be and the longer their lifespan.
In return, their descendants, through many generations of reproduction, will gradually degenerate, lose the strength and intelligent inherited from their ancestors.
The ancestors also could not reproduce much because it would reduce their lifespan and intelligence.
After degenerating, these animals cannot just breathe air or eat plants to live like their ancestors. Some animals begin to compete for each other's territory, most animals after 9 generations from their ancestors will completely degenerate, becoming wild animals, only instincts remain, kill and eat each other to survive.
The tribe of 12 holy beasts over many generations, the population did not increase, but also decreased, which created the danger of extinction for all animals.
The 12 holy beasts know that when their descendants completely lose their intelligent, that's when their lives come to an end, but they can't find a solution to this. They often have to sleep for a long time to maintain their lifespan. This period is called the Beast Age.