Silas Lin and the Lost City of Souls Chapter 133

There is alchemy in the immortal way.

There are two types of alchemy.

One is called outer elixir, and the other is called inner elixir.

External alchemy is the use of heavenly materials and earthly treasures to refine elixirs in alchemy furnaces.

In the inner alchemy technique, one uses oneself as the cauldron, the Dantian as the true fire, the spiritual energy of heaven and earth as the elixir liquid, and then uses the Taoist heart as the material to refine a natural golden elixir.