Emerald Potion

The Drink of Despair is a mysterious potion which induces fear, delirium, and extreme thirst. It has an emerald green colour to it, and glows phosphorescently. It cannot be penetrated by hand, Vanished, parted, scooped up, siphoned away, Transfigured, Charmed, or made to change its nature in any way. It can only be drained away by drinking.

Lord Voldemort used this potion to protect Salazar Slytherin's Locket (one of his Horcruxes) within the Horcrux cave.

"Kreacher drank, and as he drank, he saw terrible things... Kreacher's insides burned... Kreacher cried for Master Regulus to save him, he cried for his Mistress Black, but the Dark Lord only laughed... He made Kreacher drink all the potion... He dropped a locket into the empty basin... He filled it with more potion..."

- Kreacher describing when Voldemort forced him to test the potion's defenses.

While its effects are not completely known, the potion would seem to cause the drinker to relive his or her most horrible memories, like in a presence of a Dementor. It did cause Albus Dumbledore to either imagine or remember horrific events from his past. His screams of "kill me" could either indicate a resurfacing of the memory of his sister's death (as in, "kill me instead") or a request to be delivered from the horrible pain he was experiencing. It also causes the drinker to become extremely thirsty, although an enchantment causes any water conjured, such as by the Aguamenti spell, to vanish immediately. This forces its victim to attempt to drink water from the Horcrux cave lake, causing the Inferi to attack.

Even though Dumbledore said he couldn't change its nature in any way, Lord Voldemort turned the potion "crystal clear" to check the locket. It may be because he alone can alter the potion's characteristics to check the Horcrux, or because he only wanted to check on it rather than remove it from the basin.

It is possible that Lord Voldemort invented this potion because it seems only he understands how to alter it. However, it seems even he could not empty the basin without drinking it, since he forced Kreacher to drink the horrendous Drink of Despair.

Behind the scenes

 * In the movie, the Drink of Despair is a completely different colour, appearing as a dark blue/purple colour.
 * Also, in the book version, Dumbledore conjured a crystal cup out of thin air to drink the potion, while in the movie version, there was a seashell-shaped cup placed on top of the basin.
 * Though unnamed on the books, films and video games, the track from the film's soundtrack which plays over the scene of Dumbledore consuming the potion is titled "The Drink of Despair". This would be a particularly appropriate name for the potion, given the morbid effect that it has on its drinker.

Appearances

 * Harry Potter and the Half-Blood Prince
 * Harry Potter and the Half-Blood Prince (film)
 * Harry Potter and the Half-Blood Prince (video game)
 * Harry Potter and the Deathly Hallows
 * Harry Potter and the Deathly Hallows: Part I