For Calcium, Siderius could easily extract it from the bonedust or bones of animals he hunted. So the binding agent was not hard to find.
The Sub Reagents included two ingredients, one with a pure Earth Element and one with a pure Water Element.
Earth provided a good base for all living beings to thrive in. In essence, Earth element fortitude oneself.
Water was necessary for all lives. It was what was needed for humans to operate. Its presence ensured a flowing state of energy.
The Reagents should be easy to replace. In this dense Rottin Woods, there should be plants that could fulfil the Reagents' purpose. Similar to how Siderius had substituted the plants for the Cindrox formula.
The most important and probably the most difficult ingredient to replace was the Husky's Heart.
