|Muggles' Guide to Harry Potter - Magic|
|Type||Spell or method|
|Features||Vow once made cannot be broken under penalty of death|
|First Appearance||Harry Potter and the Half-Blood Prince|
An Unbreakable Vow is a method of making a vow that is magically reinforced. If the vow is broken, the one who made the vow apparently dies.
In Harry Potter and the Half-Blood Prince, Severus Snape makes an Unbreakable Vow to Narcissa Malfoy. Almost all of the preparation of the Vow is mental, and it requires a third party, the Bonder, who actually casts the spell, and whose wand is used to actually provide the magical power to reinforce the Vow. For the Vow mentioned here, the Bonder is Narcissa's sister, Bellatrix Lestrange.
It appears that the vow must be worded in three parts, with the receiver of the vow making three requests, each of which must be answered with something similar to "I will". Each question results in an enhancement of the magical bond between the maker and the receiver of the vow, made visible by a thread of red light emanating from the wand of the Bonder.
Very little has been mentioned of the nature of the Vow; it is likely that the role of the Bonder is somewhat similar to the role of the Secret-Keeper in the Fidelius charm, in that the vow is locked up in the soul of the Bonder.
- Given what happens when the Secret-Keeper dies, what would happen to the maker of an Unbreakable Oath should the Bonder of that oath die?
We have been told two different things about what happens when a Secret-Keeper dies. On her web site, the author states that the secret becomes effectively frozen; everyone who knows it continues to know it but none of them can divulge it to anyone else. In Harry Potter and the Deathly Hallows, we learn that when the Secret-Keeper of a Fidelius charm dies, all those who were privy to the secret at that time become Secret-keepers in turn. There is no way to reconcile these two different interpretations, but it is possible that the first one is actually somehow based on the author's plans for the Unbreakable Vow.
Carrying this thought a little further, the Unbreakable Vow does not seem to be quite analogous, in that there can be only two parties to it, plus the Bonder, while the Fidelius charm can be opened to many people. While all parties to the Fidelius charm become central to its operation on the decease of the original center, there are only two parties to the Vow should the Bonder pass away. So if the Bonder dies, it is quite possible that the Vow remains in force; the Vow would then be Bonded by the two parties to the Vow.
This is, of course, speculation. The one Vow we see is fulfilled at the end of Harry Potter and the Half-Blood Prince, and so becomes inoperative before the death of the Bonder, Bellatrix; and in fact, one of the parties to the Vow, Snape, has died before Bellatrix does. This chain of events prevents us from learning much about the charm.