A Record of a Mortal's Journey to Immortality: They All Call Me the Old Fiend

[Mortal cultivation + no System + no cheat powers + no saintly protagonist + no harem + decisive and ruthless + intelligent protagonist]

After his family is ruined, protagonist Lin Yingqian spends ten years living as a beggar. Surviving the calamity, he glimpses the path to immortality and, despite possessing a trash spiritual root, forges a legend as an old fiend.

The five demonic sects attack the nine northern Zhou sects, who turn to the dynastic court for young men and able-bodied recruits.

Lin Yingqian, a survivor of the calamity, is swept up in it too. Captured and sent to a mine, he is found by cultivators to possess a trash spiritual root, but instead of being admitted to an immortal sect, he's put to work mining.

When the demonic path attacks, Lin Yingqian luckily escapes. During his flight, he finds a dead demonic cultivator and their storage pouch, and begins cultivating immortality.

Everyone says a trash spiritual root can't reach the Great Dao. But I will prove them wrong. I will live to make the whole world see.

If a trash spiritual root can't reach Foundation Establishment, then I'll use forbidden arts to transform into a demon and establish my foundation.