Isn't the real answer 'Journey to the West', in a spiritual sense? I'm only half-joking. The actual classic novels that define the modern genre's tropes, for better or worse, have to include 'Stellar Transformations'. Its contribution is the obsessive, granular focus on a unique cultivation method—forming a universe inside your body. That trope of a protagonist with a bizarre, OP internal pathway became a massive trend. The pacing is glacial by today's standards, and the romance is... questionable, but its influence on 'special snowflake' cultivation systems is everywhere. You see its legacy in every story where the MC's dantian or meridians are weirdly unique.