Why was there only one star?
It was very simple. This was not to be used against enemies, but to temper one's own body. If he used Nine Star Energy like Heavenly Dao Flames and Ice Energy to temper his body, wouldn't that be courting death?
The path of cultivation was about gradual progress. If one relied on powerful medicines to succeed in a single step, there would basically be aftereffects.
Don't think that this wasn't awesome. It should be known that even if cultivators reached the Core Formation Tier, they would still harvest the power of heaven and earth, and cultivate mystical power, and mystical power was the lowest grade of all energy.
Thus, the first step of the Heavenly Dragon Emperor Technique was to absorb One Star high-level energy to temper one's body. This was already very impressive.