The Alicorn
People used to beleive that a unicorn horn could neutralize poisons, among other things. Some physicians in older times created these alicorn "remedies" against ailments by making cups from the horn and having their patients drink from them. People who feared poisoning sometimes drank from goblets made of "unicorn horn." Dr. Granar Conrad pretty much summed it up the belief in the sixteenth century, when he said:
This horn is useful and beneficial against epilepsy, pestilential fever, rabies, proliferation and infection of other animals and vermin, and against worms within the body from which children faint.
Alleged aphrodesiac qualities and other purported medicinal virtues also drove up the cost of "unicorn" products such as milk, hide, and offal. Unicorns were also said to be able to determine whether or not a woman was a virgin—in some tales, they could only be mounted by virgins.
Rarer still than the unicorn's horn is the mystic ruby, called a carbuncle, which was said to be found at a horn's base. Some have said that the carbuncle is the source of a unicorn's magical powers, others that it is a concentrated essense of the horn.