Altering Spell

• Incantation: Unknown (The most well-known example, the Protean Charm, is cast non-verbally in the text)
• Pronunciation: Not applicable
• Wand Movement: Unknown
• Light: Unknown
• Effect: Magically links a group of objects so that when one is altered, all others in the group change to match it.
• Type: Charm

An Altering Spell is a category of highly advanced magic, with the most famous example being the Protean Charm. This type of enchantment is used to link multiple objects, making it an effective, albeit difficult, method for secret communication or signaling. Its power and complexity are demonstrated by its use in very different magical contexts, from student resistance groups to the darkest forms of magic.

• Dumbledore's Army Communication: In her fifth year, Hermione Granger performed a Protean Charm on a number of fake Galleons to serve as secret communicators for the members of Dumbledore's Army. She gave one coin to each member. When Harry Potter updated the date and time of the next meeting on his own coin, the serial numbers on every other coin would change to match, and the coin would heat up to alert its owner. This ingenious use of an Altering Spell allowed the D.A. to coordinate its meetings without being detected by Dolores Umbridge and the Inquisitorial Squad.
• The Dark Mark: A darker and more sinister application of this magic is used by Lord Voldemort on the Dark Marks he brands onto the forearms of his Death Eaters. When Voldemort presses his wand to the Mark of any one of his followers, all other Dark Marks burn and turn black, summoning the Death Eaters to his side instantly. This magical connection ensures that his followers are always at his beck and call.
• Marauder's Map: While not explicitly named as such, the complex enchantments on the Marauder's Map function as a continuous Altering Spell. The map constantly alters its own appearance to show a real-time representation of every person's location within Hogwarts Castle. The magic is so sophisticated that it can see through Invisibility Cloaks and identify those using Polyjuice Potion.

This type of magic is exceptionally difficult to perform. Hermione Granger noted that the Protean Charm was N.E.W.T.-standard magic, meaning it is typically taught to sixth or seventh-year students at Hogwarts. This places it among the most advanced and challenging spells a student would be expected to learn. There are no known counter-spells or simple methods to undo an Altering Spell. Given its complexity, it would likely require equally powerful and specific counter-charms to disable the magical link between the enchanted objects.

The primary named example of an Altering Spell is the Protean Charm. The word protean derives from Proteus, a sea god in Greek mythology who was known for his ability to change his shape at will. This etymology perfectly reflects the spell's effect, which causes linked objects to change their form or appearance in unison.

• The charmed Galleons for Dumbledore's Army are visually depicted in the film adaptation of Harry Potter and the Order of the Phoenix, showing the numbers shifting across the coin's edge. (film)
• In the video game adaptation of Harry Potter and the Order of the Phoenix, the Protean Charm is a spell the player can learn and use to solve puzzles, such as duplicating the movements of one object onto another. (video game)