Requirements for Evolve a Physique's Grade
Minos knew that for any human to advance the level of a Physique, there would be a need to use external resources.
After all, the evolution of a cultivator's Physique rank could be compared to two cultivation stage promotions!
Such a thing was unusual to happen, and the amount of spiritual energy required was quite large.
To give you an idea, Minos would need an amount of spiritual energy to evolve his Physique from Warrior-grade to the King-grade, approximately 15 times the amount of energy required to him reach level 50!
Such a thing could not be overcome in the usual way with the spiritual energy from crystals or ordinary cultivation.
After all, he had to make the advance at once, given that his mutant Physique had such a trait.