Mastery here is a reference to mastering self and therefore mastering the system in which this self perceives, thus able to do anything within it. Historically speaking, Mastery has been in general reference to these steps:

1. First realize that reality as reported by your senses is an artificially constructed virtuality composed of something like pixels that you yourself are, just an interference pattern in a limitless data flow;

2. Secondly, purge yourself of all impurity, and know that impurity is really just thought patterns...

http://sunofallsuns.com/page/mastery