The "Emperor's Vigor Tonic" appears to be a fictional concept, likely originating from literature, games, or other forms of media where fantastical or magical elements are present.
Origin and Rarity: The tonic might have a legendary or rare status within its fictional universe, often associated with royalty, powerful figures, or ancient alchemical knowledge.
Side Effects: As mentioned earlier, the tonic typically comes with side effects or risks, which can range from temporary weaknesses after its effects wear off to more severe consequences such as addiction, magical imbalance, or ethical dilemmas.