Bezoar

A bezoar is a stone that is taken from a goat's stomach and is an antidote to most poisons. It is fairly rare, however, and does not work on everything. There is a small stock of bezoars in the Potions classroom store cupboard. Severus Snape asks Harry Potter where to find a bezoar in Harry's first Potions class; when Harry is unable to answer this or any of the teacher's other questions, he earns Snape's contempt. Three years later, in a Potions exam, Harry forgets to add a bezoar to his potion, because he was thinking about asking Cho Chang to the Yule Ball. This earns him bottom marks.

As a student at Hogwarts, the Half-Blood Prince wrote "Just shove a bezoar down their throats." across the list of antidotes in his copy of Advanced Potion-Making. During his sixth-year class about antidotes, Harry, who was unable to understand Golpalott's Third Law, fetched a bezoar from the cupboard and showed it to Professor Horace Slughorn as the answer to the poison he was supposed to be analysing. This gained Harry Slughorn's admiration and ten points to Gryffindor for "sheer cheek".

On March 1, 1997, Ron Weasley was poisoned when he drank some oak-matured mead that was intended for Professor Dumbledore. Harry, remembering the above mentioned incident in Potions class, quickly found the bezoar he had given Professor Slughorn and shoved it down Ron's throat, saving his life.

Etymology
The word "bezoar" comes from the Persian pâdzahr (پادزهر), which literally means "protection from poison."

Appearances

 * Harry Potter and the Philosopher's Stone
 * Harry Potter and the Philosopher's Stone (film)
 * Harry Potter and the Philosopher's Stone (video game)
 * Harry Potter and the Goblet of Fire
 * Harry Potter and the Half-Blood Prince
 * Harry Potter and the Half-Blood Prince (film)
 * Harry Potter and the Half-Blood Prince (video game)