In the Immortal Ancient Era, there actually weren't any realms like blood transport or Cave Heaven.
If one wanted to cultivate at that time, one needed to plant a Taoist Seed within their body.
Using a Perfect Seed as a medium, one could attempt to touch the Great Dao, comprehend the intricate principles between Heaven and Earth, and once challenges were accumulated to a certain degree, use it as a basis for impact.
The rarer the Taoist Seed, the greater the achievement when merging with the Dao.
In that era, some people used the sun, moon, and stars as seeds, some people used plants as seeds, some used great mountains and rivers as seeds, there were even some that used the Hongmeng Purple Qi as a seed.
With a hundred schools of thought contending, and all varieties of theories flourishing, there was nothing you could not think of, nothing that could not serve as a seed.