Alchemy, the first-grade Huanglong Pill, the third-grade Quchen Pill, and the fifth-grade Soul Purifying Pill
After the spirit beast's experience value is full, there will be an evolution key next to the experience value. Just feed the elixir there.
The method of evolving spiritual beasts on the Road to Immortality is indeed a difficult point in the game. I believe everyone will understand how to evolve the spiritual beasts on the Road to Immortality after reading it. The game is indeed very interesting and worth playing.