John William Polidori's Bookcase

Origin
Polidori was a writer famous for his short story The Vampyre, which is the basis of the vampire genre of fiction and the first modern story. He was friends with Lord Byron and participated in his challenge to write a horror story while on vacation; the meeting also included Mary Shelley, who famously wrote Frankenstein while she stayed with them.

Effects
Those affected will be able to smell and taste blood from miles away, allowing them to detect the presence of people or animals by the size and shape of their circulatory system. They can also identify blood disorders or additives in the bloodstream by the different tastes and smells they receive.

Unfortunately, when nearby people, the user will develop an insatiable hunger for the dissolved nutrients within their veins, along with any iron and oxygen they can receive in the process. The user will turn into a cannibalistic lamprey, sucking the user bone dry out of all their blood and bodily fluids if not stopped within time.