The Nascent Soul Level.
Some cultivators divided the eight stages of the Qi Refinement level into the upper and lower four stages. The Qi Refinement, Connate, Golden Core and Nascent Soul levels were the lower four stages, while the Soul Formation, Void Returning, Dao Reunion and Tribulation levels were the upper four stages.
The Nascent Soul level was the highest stage among the lower four. After going further from that step, cultivators would be truly the kings among the others and could be called high-level Qi Refinement Cultivators. Although the imperishable sects had tons of Nascent Soul Cultivators, only several of them among billions of people on a planet would be able to reach higher levels. Those were the Ancestral Patriarchs of a race or a sect.
There was a saying in the universe: "Nascent Soul is easy to cultivate, Soul Formation is difficult to complete."