The Celestial Beast bloodline had been plunging downward for several generations already. Back when Dyon first met his master, a bit later, he learned that the marriage between her and Zaire's father hadn't been so simple. The matters surrounding this were related to how Dyon and the Daiyu Clan became enemies. This was because his master, Esmeralda, had been promised to the Daiyu line.
However, Zaire's father won in the end, thus resulting in a blood enmity.
This was all to say that the reason Esmeralda's marriage had been arranged in the first place was as a last effort to raise the Celestial Deer bloodline. Luckily, Zaire's birth succeeded, resulting in a King of King Beasts. Unluckily, Zaire was just one person. His mission wouldn't technically be fulfilled until he became a breeding stallion for the Celestial Deer Clan.