Fantasy: the Supreme God of Killing

The Daqian Dynasty relied on martial arts to establish the country and respected martial arts. Refining the meat, refining the skin, refining the bones, refining the lungs, washing the hair and cutting the marrow, and exchanging blood. The cultivation of a martial artist cannot be achieved overnight, but only after decades of hard work can one achieve something. What? I have a plug-in! Can you consume lifespan to improve your martial arts level, or can you gain lifespan by killing enemies? Then this day, you can step on it!