New year, new start. Yiyuan Elixir was an extremely pure elixir that contained the Qi vitality of heaven and earth. Cultivators may have cut off themselves from consuming food but they would meditate in replacement of diet.
Consuming the Yiyuan Elixir could simplify the process of Qigong practice as it would provide the pure Qi of vitality for the cultivator. Furthermore, if a lowly-experienced cultivator were to take it regularly for a long-term, the elixir could improve his fitness level.
The Yiyuan Elixir was not considered as a spiritual medicine. It was just a clump of concentrated Qi of vitality of the heaven and earth.
Any cultivators who have mastered Qiaodong would be able to produce this elixir. However, most cultivators of that level would not even have enough time for their Qigong practice and meditation, let alone making elixirs. Furthermore, it would require a lot of effort to digest the Yiyuan Elixir.