Second Order vs Fourth Order
The 9-Headed Immortal Dragon was a terrifyingly powerful creature. Even at birth he was born as a level 30 First Order dragon.
Although unlike humans and other creatures that had been born and grown up by the time the Soul Record reached their worlds the 9-Headed Immortal Dragon was born in an already evolved world, being born as a level 30 dragon was definitely a great help to survive.
It was difficult for him to level up, but more difficult to advance from one Order to the next.
This was because each and every one of the classes that the 9-Headed Immortal Dragon had were Special classes, the only exception being the fourth one which was a Unique class!
Wasn't Bai Zemin aware of how difficult it was to complete the evolution requirements of a Unique class? Even the requirements to obtain Special classes were terrifying; he knew this from his subordinates and friends.
But, everything had its reward.