The martial arts heritage of the Heavenly Martial Realm runs deep, with a vast, boundless ocean of martial techniques and divine arts sufficient to occupy a cultivator for the entirety of their thousand- or ten-thousand-year lifespan.
As for the techniques and manuals derived from heterodox paths, they are all classified as forbidden books. The Heavenly Martial Realm requires cultivators who will grow into top-tier martial powerhouses, not "turncoats" who study techniques from higher realms only to defect in pursuit of an ultimate Dao. The imperial family of the Sacred Martial Empire goes without saying; to ensure the legitimacy of their bloodline and status, they would never permit their princes or princesses to practice "heterodox" arts. Exposure to such knowledge might lead them to question the martial philosophy they were indoctrinated with since childhood, causing them to stray from the righteous path.
Having been in the Heavenly Martial Realm for some time, Chen Xuan, despite never having visited the main star, had gained a rough understanding of the Sacred Martial Empire.
Chapter 3541