Dissendium

• Incantation: Dissendium
• Pronunciation: dis-SEN-dee-um
• Wand Movement: Tapping the target object.
• Light: None described.
• Effect: Functions as a magical password to open the secret passage located in the statue of a one-eyed, humpbacked witch on the third floor of Hogwarts Castle.
• Type: Charm

The only known use of this incantation in the novels occurs in Harry Potter and the Prisoner of Azkaban. After being denied permission to visit Hogsmeade, Harry Potter is given the Marauder's Map by Fred Weasley and George Weasley. The map reveals a secret passage to the wizarding village, one of seven leaving Hogwarts Castle. The entrance to this specific passage is a stone statue of a one-eyed witch. The Marauder's Map instructs the user to tap the statue with their wand and speak the password, “Dissendium”. Upon doing so, the witch's hump slides open to reveal a large hole, leading to an earthy slide that ends in the cellar of Honeydukes sweetshop in Hogsmeade. Harry Potter successfully uses this password and passage to sneak into Hogsmeade on multiple occasions during his third year. While he is often accompanied by Ron Weasley and Hermione Granger, Harry is the only character explicitly described as using the incantation.

“Dissendium” is not taught in any known Hogwarts class. Its use is learned exclusively from the instructions provided by the Marauder's Map. The magical effect appears to be tied entirely to knowing the correct word and procedure, rather than requiring any particular level of magical skill. There are no known counter-spells or methods to magically disable the passage entrance. The passage itself can be physically blocked from the inside of the Honeydukes cellar, as the trapdoor can be bolted.

The word “Dissendium” is likely derived from Latin. It may be a portmanteau of the prefix `dis-`, meaning “apart” or “away,” and the verb `descendo`, meaning “I descend” or “I go down.” This combination aptly describes the spell's function: to open something apart so that one may descend. Alternatively, it could be related to the Latin noun `dissidium`, which means “separation” or “disagreement,” alluding to the separation of the witch's hump from the main statue.

• In the film adaptation of Harry Potter and the Prisoner of Azkaban, this secret passage and the incantation “Dissendium” are omitted. Fred Weasley and George Weasley simply show Harry Potter the passage without any mention of a magical password (film).
• In the Harry Potter and the Prisoner of Azkaban video game, “Dissendium” is a learnable spell that functions more generally to open secret doors and reveal hidden areas throughout Hogwarts Castle, not just the one-eyed witch passage (video game).