I got into the manga a few months back after bingeing the Donghua. The core trio is pretty established: Lin Dong, Lin Qingzhu, and Ling Qingzhu. Lin Dong's the classic underdog protagonist from a minor branch family, but his drive is insane. He's always pushing himself with that stone talisman. Qingzhu starts off as this almost mythical, icy figure from the Lin Clan, way out of his league, but their dynamic changes a lot as the story goes on. Then there's the third, Little Flame, the little marten beast he picks up early on who becomes a brother-in-arms. You can't forget Yao Lao either, the elderly spirit in the stone talisman who guides him – that mentor-student bond is central to the whole cultivation journey.
Some of the side characters have real staying power too. Lin Langtian, the arrogant genius from the main family, is a great early rival. The Heavenly Flame Fairy, that fiery entity, adds a whole other layer of power and mystery later. The cast expands massively as he moves into new realms, but it always comes back to Lin Dong's core group and his unwavering determination to protect them.