Becoming a Third-order Alchemist or Artifact Refiner isn't too difficult.
But if you wish to continue progressing, and even reach the Fourth-order, the amount of effort, energy, and time required is unimaginable.
In the Central Continent World, the highest level was the Second-order Cultivator, but occasionally you'd see Third-order Alchemists and Artifact Refiners.
However, in the Starry Sky World, Third-order Divinity Transformation cultivators were common, Independent Immortals were numerous, and there were even Fourth-order Great Powers as well as Eleventh Tribulation Independent Immortals comparable to Fourth-order cultivators.
Yet, during Chen Jichuan's 20,000 years of roaming in the Starry Sky World, he had never encountered a single Fourth-order Alchemist or Artifact Refiner.
It shows how difficult this pursuit truly is.
