The move taught by Duan Tie is naturally a secret Primordial Spirit Technique of the Blood Talisman Divine Sect, called the Beheading Soul Splitting Technique. As the name suggests, it involves condensing one's Divine Soul to transform into a Blood Blade, and with one slash, cutting the opponent's Primordial Spirit into two segments, decimating their Divine Soul utterly. Although the move is simple, it excels in its simplicity and practicality, using the most primal killing intent to destroy the opponent's Daoist Heart.
Though not exactly a Heavenly Book Divine Skill, it is nonetheless a secret technique that usually requires earning a Third-class Merit to exchange for, but now it's essentially given to Chen Xuantian for free.