Gu Zhen Ren
If you think about it, everything Fang Yuan has on him, has been earned by him. Not because he's special, unlike most of the other Novels where the MC gets the best of both worlds just because he's special in some way or walk-in to an old site and gets the supreme inheritance. Even the Spring Autumn Cicada was refined by him after spending countless years into the research and sacrificing numerous mortals. He is not lucky, but he is one tough scheming bastard who gets what he wants. Today also he schemed against the Fairy into giving access to her Gu worms on her own accord.
How can fang yan use other's immortal essence ? its stated that only the person producing the essence can use that essence. its a mere will of rank 9. but even after many thousands of years of decay, dividing many times, many tribulations, gu taken away from the will by the hand, loosing its essence, its still way more powerful than rank 6. but a rank 6 immortal himself cant hold a candle to rank 5 mortal ...... where its stated that rank 5 to rank 6 is qualitative change .