Polyjuice Potion

Polyjuice Potion is a very complicated potion that allows the drinker to assume the form of someone else. While it can account for both age and gender, Polyjuice Potion cannot be used for a human to take an animal form or for a half-breed to assume human form. It was used many times in the events leading up to, and during, the Second Wizarding War (and possibly the First Wizarding War, although there are no documented instances of it). The potion also played a crucial role in Harry Potter, Hermione Granger, and Ron Weasley's investigation of the Chamber of Secrets in their second year. It was also used in Draco Malfoy's plot to smuggle Death Eaters into Hogwarts School of Witchcraft and Wizardry in 1997, in the Battle over Little Whinging, and in Harry, Ron, and Hermione's break-in of Gringotts Wizarding Bank in 1998.

Ingredients

 * 1) 12 lacewing flies that have been stewed for 21 days
 * 2) 1 ounce of crude Antimony
 * 3) 4 leeches that have been "unsucculated"  (which presumably means their suckers have been removed)
 * 4) 16 scruples of fluxweed that was picked at full moon
 * 5) 3 drachms of pulverised Sal Ammoniac
 * 6) Pulverised blades of knotgrass
 * 7) 1 pinch of powdered horn of a Bicorn that has been "lunar extracted"  (which presumably means that, like the fluxweed, its collection time coincided with certain lunar conditions)
 * 8) Filings and rasplings of Salpeter, Mercury and Mars ("filings of Mars" may mean iron filings, as the symbol for the planet Mars, ♂, is also used to signify the element of iron )
 * 9) Shredded dried skin of a Boomslang
 * 10) Extract of The-Transfigured-Being-To-Be  (which means a piece of the person one wants to change into, typically hair)

Most of the ingredients are available in the students' cupboard at Hogwarts, although some of them are only available in Severus Snape's private stores. It takes at least two to three months to brew properly.

Appearance
A piece of the person who is to be imitated — usually hair — is needed for the transformation. Before this final ingredient is added, Polyjuice looks like thick, dark mud that bubbles slowly. When the piece of the person to be imitated is added, however, the potion changes colour; it seems to react according to the nature of the person to be imitated, once even described as the 'essence' of the person. Good-hearted people result in more attractive colours and tastes, while mean people cause the opposite effect. Harry Potter's was a pure golden colour, whereas Gregory Goyle's tasted like "overcooked cabbage" and "looked like bogies" , Bellatrix Lestrange's tasted "disgusting, worse than Gurdyroots" and Mafalda Hopkirk's was a pleasant heliotrope colour. It is likely that the taste differs from potion to potion, though everyone doubles over in pain when they drink it.

Effects
"“Ooh, you look much tastier than Crabbe and Goyle, Harry,” said Hermione, before catching sight of Ron’s raised eyebrows, blushing slightly, and saying, “Oh, you know what I mean – Goyle’s Potion looked like bogies.”"

- Before Hermione Granger took on Harry's appearance for the Battle over Little Whinging

The effect lasts for an hour, but as Barty Crouch, Jr. proved when he kidnapped and impersonated Alastor Moody for an entire Hogwarts school year, continual dosing can draw out the effects indefinitely. If a person dies while under Polyjuice Potion, as Mrs. Crouch did, then they will retain the form of whoever they have transformed into, rather than reverting back to their original shape.

Polyjuice can be used by a person to transform into someone of the opposite gender. It appears to adapt to account for the age of the person being turned into, as well as any injuries they have acquired, as Barty Crouch, Jr. needed a magical eye and wooden leg when he used the potion to turn into Alastor Moody. In addition, congenital conditions the person being turned into has will apparently be replicated, as Hermione Granger required spectacles to see clearly after turning into Harry Potter.

The potion is complicated and can go awry. For example, when Hermione brewed Polyjuice in her second year, she intended to take the form of Millicent Bulstrode, but she mistook a cat's hair for Millicent's hair. The resulting potion caused Hermione to partially transform into a cat. As the Polyjuice Potion cannot be used to successfully transform into an animal, Hermione's change did not reverse after an hour. She went to the Hospital Wing and did not recover until after the winter holidays.

Likewise, the potion cannot be used by a non-human or half-breed individual to turn into a human, as Remus Lupin informed the half-giant Rubeus Hagrid. However, it seems that individuals whose non-human ancestry is less than half can successfully use Polyjuice, as quarter-Veela witch Fleur Delacour transformed into Harry Potter in 1997. However, it is also possible Lupin meant that a person cannot transform into a half-breed using Polyjuice Potion, but half-breeds themselves can.

Search for the Heir of Slytherin


In their second year, Harry Potter, Ron Weasley, and Hermione Granger came to suspect that Draco Malfoy was the Heir of Slytherin. To investigate this, they planned on taking on the form of Slytherin students and questioning Malfoy. Hermione used an autograph of Professor Gilderoy Lockhart to enter the library's Restricted Section so as to find the potion's ingredients, then stole them from Professor Snape's cupboards, and brewed the advanced potion. While Harry and Ron successfully transformed into Gregory Goyle and Vincent Crabbe respectively, Hermione's potion went wrong, as previously mentioned.

Barty Crouch Jr.
Between September of 1994 and June of 1995, Barty Crouch Jr. used Polyjuice Potion to take on the appearance of Alastor Moody, Hogwarts' new Defence Against the Dark Arts professor, in order to enter Harry Potter into the Triwizard Tournament as part of Lord Voldemort's plot to return to power. Throughout the year, Crouch stole the potion's ingredients from Severus Snape's cupboards, leading Snape to suspect that Harry himself was behind the theft. Crouch was eventually exposed.

Plot Against Dumbledore
After Horace Slughorn showed a cauldron of the Polyjuice Potion to his first N.E.W.T. Potions class, Draco Malfoy stole some, and forced Gregory Goyle and Vincent Crabbe to use it continuously throughout the 1996–1997 school year. They would stand watch outside the Room of Requirement disguised as young girls, while Malfoy repaired a Vanishing Cabinet inside, as part of his assignment to assassinate Albus Dumbledore and let Death Eaters into Hogwarts.

Battle of the Seven Potters
"Fourteen of us won’t be flying to Tonks’s parents. There will be seven Harry Potters moving through the skies tonight, each of them with a companion, each pair heading for a different safe house."

- Alastor Moody on the plan to move Harry to safety in 1997

The Order of the Phoenix made use of Polyjuice in 1997 in order to safely remove Harry Potter from 4 Privet Drive before his seventeenth birthday. Six people — Hermione Granger, Ron Weasley, Fleur Delacour, Fred and George Weasley, and Mundungus Fletcher — impersonated Harry in order to act as diversions when they were ambushed by Death Eaters. Soon after, Harry himself used it to disguise himself as "Barny Weasley" at Bill Weasley and Fleur Delacour's wedding.

Infiltration of the Ministry and Gringotts Break-In
The trio used Polyjuice that they stole from Moody to infiltrate the Ministry of Magic to search for Salazar Slytherin's Locket in September of 1997. Harry, Ron and Hermione disguised themselves as Albert Runcorn, Reginald Cattermole, and Mafalda Hopkirk, respectively.

The following year, Hermione used the remaining Polyjuice Potion again as part of the trio's plan to break in to Gringotts in order to retrieve Helga Hufflepuff's Cup from the Lestrange Vault. Using a strand of Bellatrix Lestrange's hair that had fallen on her sweater while Bellatrix interrogated her at Malfoy Manor, Hermione assumed her form. However, there wasn't enough, so Ron had to simply use cosmetic design to disguise himself.

The lack of suspicion in anyone in all these incidents leads one to the understanding that Polyjuice Potion is very uncommon. Granted, Severus Snape knew someone was stealing the ingredients from his cupboards and suspected Harry Potter, but that is more indicative of Snape's eagerness to blame Harry for anything than any actual guilt.

Behind the scenes

 * In the film version of Harry Potter and the Chamber of Secrets, Polyjuice Potion does not cause the drinker's voice to change as well as their appearance. However, Barty Crouch Jr's voice does change to Moody's in Harry Potter and the Goblet of Fire (film). However, it is possible he could have just been imitating Moody's voice. It does say, however, in the book version of Chamber of Secrets, that Harry, Ron and Hermione's voices change after taking it.
 * The name 'Polyjuice' probably comes from the Greek poly, meaning "many".
 * In the video game version of Harry Potter and the Prisoner of Azkaban Draco Malfoy uses the potion to turn into Ron to trick Harry into following him into a trap to find Sirius Black.

Appearances

 * Harry Potter and the Chamber of Secrets
 * Harry Potter and the Chamber of Secrets (film)
 * Harry Potter and the Chamber of Secrets (video game)
 * Harry Potter and the Prisoner of Azkaban (video game)
 * Harry Potter and the Goblet of Fire
 * Harry Potter and the Goblet of Fire (film)
 * Harry Potter and the Order of the Phoenix
 * 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

Notes and references
Polynectar