What were the major determining factors of a dragon's strength?
There were many factors one could consider, such as the density of their scales, the strength of their aura, or the density and sheer amount of their mana. However, the factors everyone could understand and all could agree on were the quality of their bloodline and their bloodline ability.
Naturally, those with the purest bloodline were the royal family, and below them were the clan families.
Among all others, the quality of a dragon's bloodline and their bloodline ability could almost be considered the core determinants of a dragon's strength. But there have been many cases in dragon history where those with a poor bloodline or weak bloodline ability rose to possess strength that easily rivaled the celestials.