At least some content in this article is derived from information featured in Harry Potter: Hogwarts Mystery. Spoilers will be present within the article.
The Sleepwalking Curse (Incantation unknown) is a curse that is used to put an individual into a deep sleep from which they may never awaken, inducing a condition similar to that of somnambulism. This specific curse was placed on one of the five fabled Cursed Vaults, the Forest Vault, prompting the victims to mindlessly wander off into the Forbidden Forest, where the entrance to the Cursed Vault in question was believed to be located. Unable to defend themselves in such an exhausted state, some were ravaged and devoured by the dangerous creatures within.
At some point in the history of Hogwarts School of Witchcraft and Wizardry, a Cursed Vault hidden within the Forbidden Forest was tampered with, which activated the Sleepwalking Curse. The curse caused students at the school to wander unconsciously into the Forbidden Forest, where an Acromantula was waiting to devour them. In the early 1980's, the incidents of students sleepwalking into the forest increased dramatically, prompting Jacob's sibling to search for the vault and break its curse.