Who Can Slay Demons When They Are Invincible?

In the Daning Dynasty, the world was filled with demons and evil spirits. Lu Chen, who traveled through time, obtained the "Demon Slaying" system, which allowed him to kill demons, intercept the remaining life span, and consume his life span to unlimitedly deduce martial arts. But the problem is, Lu Chen discovered that his predecessor was Lao Liu. Although he was unknown, he was actually a great sage who killed demons and was proficient in all martial arts. Then I still have to deduce something! According to the novice mission issued by the system, Lu Chen crushed a dog demon to death out of boredom... Lu Chen [Current lifespan: nine hundred and sixty-six years] [Kill the intelligent dog demon, the total life span is 121 years, and the remaining 19 years are absorbed] Current Martial Arts [The art of drawing swords (Dzogchen)] [Demon-Suppressing Sword Technique (Dzogchen)] [Emperor's Killing Fist (Dzogchen)] [Beidou Youlongbu (Great Perfection)] ………… [The Supreme Forgetting Love Record (Great Perfection)] [Six Paths of Reincarnation and the Immortal Demon Power (Great Perfection)] One Finger of Jiangshan (Dzogchen) [Nine Cuts of the Void Sword Technique (Dzogchen)]... ………… [You have mastered all martial arts and cannot continue to infuse the demon Shouyuan deduction] [Therefore: the demon's life span can be converted into one's own life span] ………… In this world, the lifespan of a mortal is only a hundred years. Even for the divine dynasty above the clouds, a saint as terrifying as Lu Chen, a thousand years is the end! "Can't Shouyuan transform himself by deducing martial arts?" "This is a great gesture. System, please help me convert all of it into my own longevity... Thank you." You kill monsters, get promoted and make a fortune, and become famous. I, Lu Chen, slay demons and only seek—immortality! [This book is nonsensical, has no routines, is relaxed and joyful]