The answer to joining the Three Supreme Races lies in the Trivy League:
A competition held once every hundred years, where the greatest talents of the most supreme races in the Upper Realm gathered to compete.
Afterward, they could earn the approval of those from the Three Supreme Races, who would then take them in for further training.
Only the most prodigious of geniuses were chosen, and the way to enter the competition wasn't fixed.
There was a seal card called the Trivy Card, already given to some powerful families in the Upper Realm, which they could bestow upon their students or other races they found appealing.
Some of the geniuses in these families already held the card.
Seizing the card from a genius who already held it was one way to join the competition.
The Trivy League didn't exactly care who held the card, only who brought it to them before the Final Phase of the competition started.
