When cultivators begin to cultivated Heaven and Earth energy, their dantian and meridians adapt to the cultivation method they practice. If a cultivator follows the orthodox path, their energy will be shaped accordingly. If they practice demonic cultivation, their energy will be molded into demonic energy, and so on.
This is fundamental knowledge and an absolute rule in the world of cultivation. What if you want to switch from orthodox to demonic cultivation? You would need to completely rebuild your dantian and meridians to accommodate the new energy.
Such an endeavor requires immense resources and an iron will because destroying your own cultivation means erasing a lifetime of hard work. Moreover, losing your cultivation can lead to death, as without it, your body's natural lifespan will quickly catch up, slowly deteriorating without the energy to sustain its functions.