At the start of the Emperors Era it was practised by Min Ren. Later, when he became an Immortal Emperor, he reminisced about this technique. He once again cultivated with it, slowly perfecting it. Of course, as a Martial Art, it was not comparable to the Immortal Emperor Merit Laws that he created, let alone the Heaven's Will Secret Law, but it was still very powerful.
For some reason Min Ren didn't wanted for his descendants to practice the Invisible Dual Blades, so the technique had lied dormant in the library of the Cleansing Incense Ancient Sect for millions of years as no one knew its real power.
After Li Qiye joined the Cleansing Incense Ancient Sect, since he knew the truth about the Invisible Dual Blades, he requested access to it. Cultivators considered martial arts to be weaker than even the simplest Merit Law, so the Elders gladly agreed, and the manual was given to Li Qiye.