For several years after the defeat of the Dark Lord Voldemort, the Wizarding World and Hogwarts itself has been peaceful. Even though there may be Death Eaters that remain, Hogwarts has remained safe for its students and teachers.
Lately, however, something had been disturbing the Magical Creatures that reside in the Forbidden Forest at the edge of the School grounds. The Centaurs, once plentiful enough to guard the forest against unwanted threats, have seemingly vanished. Acromantulas have been spotted at the entrance of the forest, growing closer to the castle.
Unicorns have fled as well, and those who can see them say even the Thestrals have been bothered as of late.
The Ministry of Magic has been looking into this and asks that all student and personnel stay away from the first for the time being. Care of Magical Creatures classes will be suspended until further notice.