Fidelius Charm

The Fidelius Charm is a powerful spell used to conceal secrets, ranging from secret identities to entire buildings. The caster of a Fidelius must appoint another wizard or witch their Secret Keeper. Said Secret Keeper would be the only one able to share the Secret with others, but could only do so voluntarily.

## Limitations

While the Fidelius is powerful, it is not without limits. Intricate ward schemes can prevent the use of a Fidelius, which is part of the reason why the Potters did not cast a Fidelius on their family manor, the other being its size.

A Fidelius's Secret Keeper can only share the Secret voluntarily, and the spell also prevents them from taking magical secrecy vows related to the Secret, forcing the caster to put their complete faith in their Secret Keeper. It is also impossible for a single person to be the Keeper or caster of multiple Secrets.

If a Secret Keeper dies but has a magical portrait, said portrait can still act as Secret Keeper.

## History

### Early Twentieth Century

At some point after creating his first Horcrux, Lord Voldemort made the soul fragment living within the Diary the Secret Keeper of the fact that Tom Riddle and Voldemort were one and the same. The soul fragment was just different enough from Voldemort in terms of personality that magic considerd it to be a different person. The placing of this Fidelius modified the memories of many who had known Tom Riddle, including Albus Dumbledore, who very firmly remembered that he thought Riddle should not be hired at Hogwarts in any capacity, but could not for the life of him remember why.

Voldemort also hid the location of the Gaunt shack under a Fidelius, as he had hidden one of his Horcruxes there. He appointed high-ranking Death Eater Erasmus Wilkes as the Secret Keeper of this Fidelius.

At some point before the 1990s Aberforth Dumbledore cast a Fidelius that hid the fact that he and Albus Dumbledore are brothers.

### First Wizarding War

Lord Arcturus Black possessed knowledge of a modified Fidelius Charm, which was not as powerful but did not appear to require a Secret Keeper, which allowed his grandson Regulus Black to fake his death in 1979.

In early 1980 Voldemort learned of a prophecy uttered by Sybill Trelawney, foretelling the the rise of "*The one with the power to vanquish the Dark Lord*". Albus Dumbledore believed this to refer to one of the children of James and Lily Potter or Frank and Alice Longbottom, and by the time that Voldemort had reached the same conclusion Dumbledore had already sent the two families into hiding.

James and Lily moved into a cottage in Godric's Hollow. They originally planned to name their friend Sirius Black as their Secret Keeper, but Peter Pettigrew, who had by this point been spying on the Order of the Phoenix for Augustus Rookwood for months, convinced them to make him their Secret Keeper instead while letting their allies think it was Sirius. Peter used his position as Secret Keeper to sell out the Potters to Voldemort in exchange for a high position in Voldemort's council. When Voldemort is seemingly killed by Jim Potter Peter uses an Unspeakable potion to alter James and Lily's memories and make them think that they truly made Sirius their Secret Keeper.

### Book 1 - The Prince of Slytherin

Harry Potter theorises that the Philosopher's Stone's true location is outside of Hogwarts, with Nicolas Flamel having cast a Fidelius with his wife Perenelle as his Secret Keeper.

### Book 2 - The Secret Enemy

Voldemort's true identity is revealed to Harry and Jim Potter and Ron Weasley in the Chamber of Secrets, and the destruction of Tom Riddle's Diary leaves Harry and Jim as its new Secret Keepers. Jim informs Albus Dumbledore, Rufus Scrimgeour, and James Potter, while Harry later informs Regulus Black and Lucius Malfoy of Voldemort's true identity.

### Book 3 - The Death Eater Menace

Dumbledore begins experimenting with the Fidelius Charm to test its limits, hiring Remus Lupin at Hogwarts under the fake identity of Malachi Sturgeon. Ron Weasley, who has to be let in on the Secret, is able to notice the similarities between Malachi Sturgeon and Brother Chandra, a name Remus used at Shamballa, but his also appears to have the effect of making him forget that Remus is Chandra. To continue their experiment Dumbledore has Remus reveal part of the Secret, that Malachi Sturgeon is Remus Lupin, to Harry while keeping another part, that he is a werewolf, a secret from Harry. Dumbledore wishes to see if Harry can use his gift for deduction to figure out the second part of the Secret. Harry is unable to figure this out despite others telling him to his face multiple times.

While discussing the prophecy and their wands shortly after the Hogsmeade attack, Harry and Jim come to the disturbing realisation that Garrick Ollivander was aware of which wand Voldemort owned despite having sold said wand to Tom Riddle.

Harry reveals Voldemort's Secret to Theo No-Name and Blaise Zabini, and the three boys experiment with revealing parts of the Secret to Amy Wilkes, Ginny Weasley, and Luna Lovegood. Blaise and Theo tell them that Tom Marvolo Riddle was the son of a Muggle and a Squib who attended Hogwarts, and that the same is that the same is true for Voldemort. While the three girls are able to retain the information, they are unable to come to the conclusion that Riddle and Voldemort are one and the same. Luna briefly voices shock that Voldemort's middle name is Marvolo, but seems to forget this information seconds later.

When Peter Pettigrew visits Hogwarts Remus decides to reveal the Secret to him, wishing to discuss his recent discovery that the Unspeakables had tampered with their memories while they were at Hogwarts.

In a timeline erased by Harry, Peter Pettigrew reveals the full secret to Harry and James Potter while he is holding them captive in the Shrieking Shack. In this timeline Harry is forced to kill Remus Lupin in self-defence, which causes the Fidelius to collapse. When Harry travels back in time using the Time-Turner he is able to avert Remus's death and cure his lycanthropy by helping him embrace the fact that he is a natural wolf Animagus, which he had suppressed from childhood. This also causes the Fidelius to collapse, as Remus Lupin is no longer a werewolf.

With the collapse of the Malachi Sturgeon Fidelius Dumbledore makes Remus the Secret Keeper of a new Fidelius containing several ingredients of Damocles Belby's Wolfsbane Potion to prevent Peter Pettigrew from reproducing it for Fenrir Greyback.

During the school year's final meeting in the Prince's Lair, Harry reveals the full secret to Amy Wilkes and Ginny Weasley, while also sharing his theory that Rian O'Grady was another one of Voldemort's aliases.

### Book 4 - The Resurrection Game

Harry uses Metamorphmagery to disguise himself as Erasmus Wilkes's son to find out more about Voldemort's Horcruxes from his portrait. Wilkes's portrait reveals the Secret of the location of one of the Horcruxes to Harry, believing Harry to be working towards Voldemort's resurrection. Wilkes also nearly refers to Voldemort as Tom multiple times throughout the conversation.

When they are cornered by Tiberius Nott during the riots at the Quidditch World Cup, Theo makes Harry reveal Voldemort's true identity to Tiberius, and uses that and Harry's theory that Rian O'Grady was Voldemort to goad Tiberius into attacking him. Doing so makes Tiberius break an Unbreakable Vow, causing him to lose his magic and be attacked by his own Barghest, who considers him to be a squib.

## Behind the Scenes

* The Fidelius cannot be used on a fact that is already known by a critical mass of people. Dumbledore was able to hide that "Malachi Sturgeon is the werewolf Remus Lupin", but would not be able to hide that "Remus Lupin is a werewolf", which can be seen in the fact that everyone who knew Remus was a werewolf still knew so despite the Fidelius

## References

Book 1 - HP&PoS - Ch. 9 - Study Sessions,

"[A] sworn statement from an Unspeakable... ...giving expert testimony that a Fidelius Charm could only be penetrated if the secret keeper voluntarily revealed it...".
Book 2 - HP&TSE - Ch. 41 - Countdown to a Birthday,

"Besides, a Fidelius on the Manor would not have worked properly anyway because of its size and extensive ward scheme, so we still thought Godric's Hollow was safer.".
Book 2 - HP&TSE - Ch. 68 - A New Year Begins.
Book 3 - HP&DEM - Ch. 98 - Feasts, Electives & Student Organizations (Pt 2),

Malachi Sturgeon reveals his true identity to Jim Potter.
Book 4 - HP&TRG - Ch. 145 - Little Hangleton,

Harry disguises himself as a Wilkes to speak with Erasmus Wilkes's portrait.
Book 3 - HP&DEM - Ch. 105 - Chaos in Hogsmeade (Finale),

"Ollivander didn't sell a wand to Voldemort. Ollivander sold a wand to an 11-year-old Tom Riddle, but it was Voldemort who used it against you.".
Book 2 - HP&TSE - Ch. 78 - The Riddle of the Diary,

Dumbledore discovers the Fidelius Charm tied to Tom Riddle's diary.
Book 2 - HP&TSE - Ch. 80 - Three Princes,

Harry reveals Voldemort's true identity to Regulus Black and Lucius Malfoy.
Book 3 - HP&DEM - Ch. 100 - The Persistence of Memory,

"Oh come on! It's obvious! He's Brother Chandra!".
Book 3 - HP&DEM - Ch. 114 - The Blackest Day (Pt 3),

Harry reveals the Secret to Walburga Black, which leads her into a disturbing rant about the Unbroken Chain.
Book 3 - HP&DEM - Ch. 117 - The Month of January,

Harry, Blaise, and Theo experiment with the Fidelius.
Book 3 - HP&DEM - Ch. 137 - The Future All Around Us, Waiting to Be Born (Pt 1),

Harry reveals his findings about Rian O'Grady in the Prince's Lair..
Book 4 - HP&TRG - Ch. 143 - A Series of Tense Conversations (Pt 1),

Harry reveals the true identity of Voldemort to the Azkabal.
Book 4 - HP&TRG - Ch. 151 - The Quidditch World Cup (Pt 6),

Theo goads Tiberius Nott into attacking him.
Book 3 - HP&DEM - Ch. 132 - Lords of the Wizengamot,

Peter convinces James to make him the Secret Keeper.
Book 3 - HP&DEM - Ch. 120 - What's Past is Prologue (Pt 2),

Remus and Peter reunite.
Book 3 - HP&DEM - Ch. 122 - The Hunting of Sirius Black (Pt 1),

Peeves reveals that he overheard "Loony Lupin's precious Secret".
Book 3 - HP&DEM - Ch. 122 - The Hunting of Sirius Black (Pt 1),

Peter reveals the true identity of Malachi Sturgeon to Fenrir Greyback using Remus's note.
Book 3 - HP&DEM - Ch. 123 - The Hunting of Sirius Black (Pt 2),

Peter reveals his true ancestry.
Book 3 - HP&DEM - Ch. 129 - Redux (Pt 3),

Harry legilimizes a transformed werewolf.
Book 2 - HP&TSE - Ch. 68 - A New Year Begins,

Harry and Dumbledore briefly discuss Tom Riddle.
Book 4 - HP&TRG - Ch. 143 - A Series of Tense Conversations (Pt 1),

"Well, for a start, I'm not the one who ensured that outside of ourselves, no one in Wizarding Britain has any idea that Aberforth Dumbledore and Albus Dumbledore are brothers!".
Book 3 - HP&DEM - Ch. 92 - Reactions & Overreactions (Pt 3),

"Anyone who knew Regulus Black would just assume I had died somehow without thinking too much about the details unless someone who knew the truth corrected them. Of course, it's not a true Fidelius, and sufficiently clever or strong-willed people can see through it...".
Book 1 - HP&PoS - Ch. 32 - The Death Eater Snape,

Snape reveals why he joined the Death Eaters.
Book 3 - HP&DEM - Ch. 134 - The Kings of Rats,

An imprisoned Peter taunts James.
Book 1 - HP&PoS - Ch. 2 - Halloween 1981,

Peter arrives at the destroyed cottage in Godric's Hollow.

"If Nicholas Flamel had really wanted the Stone protected, he'd have hidden it at the bottom of his sock drawer, cast the Fidelius with his wife as Secret Keeper, and let that be the end of it. ...Which is, of course, exactly what he did!".
Book 2 - HP&TSE - Ch. 77 - The Chamber of Secrets,

Harry and Jim face the Heir of Slytherin.
Book 3 - HP&DEM - Ch. 114 - The Blackest Day (Pt 3),

Harry is unable to figure out that Remus Lupin despire Sirius having said it mere minutes ago.
Book 3 - HP&DEM - Ch. 118 - Secrets Revealed,

Harry discusses the Fidelius with the copy of James in the Marauders' Map.
Book 3 - HP&DEM - Ch. 136 - The Fall of the House of Potter (Pt 2),

"There are three rare ingredients which must be added to the Belby formula in precise amounts for it to work. I have begun the process of preparing a Fidelius Charm so that those ingredients and their proportions will become a Secret.".