Opening the 12th palace is not realm of Dao Monarch or Myriad Dao, it is only half way.
When a cultivators opens the 12th fate palace they face a choice between creating golden body and become a Dao Monarch or become a Myriad Dao Celestial Body .
Dao Monarchs have a Golden Avatar and Primordial tree.
Celestial body is divided into 4 stages, each stage consisting of 9 circles.