Methods

 Method  Practicing a method didn't have so many requirements as practicing a secret method did. All methods aim to take in the spirits of the universe. There are only differences in characters. Those characters are obediance, willingness, pillage, and devouring.

The obedience is the most popular. Most of the methods will teach you how to communicate with the spirits of the universe, obey them and let the spirits in naturally.

The willingness is more powerful. This character will attract the spirits of the universe to come to you voluntarily.

The pillage is easy to understand as well. It means whether the spirits are willing or not, you'll take them in by pilklage.

The devouring is the most powerful and the least popular. It's quite similar to the pillage. But the pillage is such a bossy method that the spirits gotten from it are not pure enough. As a result, there will be risks as time passes. But the devouring is different. No matter if the spirits are pure or not, the devouring will convert them to pure genuine Qi and store it in the body.

The character differences of these four methods are correspondent with four levels in the Nine Heavens Continent, which are sky, earth, black, and yellow. The obedience is the yellow level and the devouring is the sky level.  Secret Method 

 Doctrine Method