Ever wanted to add a legendary artifact to your campaign, but you were worried about PC’s getting their hands on it?
Or you put the Legendary item in your game and the PC’s already managed to get it?
What to do, and how to fix it.
An alchemist enchanted his equipment to produce even more powerful alchemical compounds, potions and the like. Unfortunately, it is not well-known that he had different sets of equipment for different processes: If the wrong set of gear is used, the result will invariably fail to function. It's not a cursed item, just something that's hard to figure out.