Theriac is a noun that refers to a medicine that is reputed to cure all. 

Our word of the day comes directly from ancient Greece where it referred to the venom of a snake reputed to contain healing properties. Centuries later, doctors no longer believe in prescribing snake venom to their patients, but the term theriac is still very much around describing all manner of cure-alls. 

After getting sick, I tried a little of the theriac that my friend insists will offer an immediate cure. Not only did this so-called theriac not cure me, but it also added to my list of problems a giant stomach ache.