alcahest

Alkahest, Alcahest, al′ka-hest, n. the universal solvent of the alchemists.

Alchemy furnishes the theme for one tale; the protagonist seeks an alcahest, a human victim for his crucible.

The alcahest was his celebrated universal medicine, and was considered the greatest mystery of all.

It was then placed in a dish and set on fire, and the residue that remained was the alcahest.