The Magical Mixture is the contents of a glass jar carried by Barty Crouch Jr. while disguised as Professor Alastor Moody. The mixture is described as a murky liquid. Contained within this liquid was a live Hinkypunk, a tiny, one-legged creature that appeared as a feathery, black shape resembling a wisp of smoke.
The primary function of the Magical Mixture was to serve as a practical teaching aid in a Defence Against the Dark Arts lesson.
This specific Magical Mixture is mentioned only once in the entire series. In the autumn of 1994, Barty Crouch Jr., using Polyjuice Potion to impersonate Alastor Moody, brought the jar to his fourth-year Defence Against the Dark Arts class at Hogwarts School of Witchcraft and Wizardry. He presented it as part of his lesson plan, which focused on recognizing and combating various Dark creatures. This lesson was part of his larger, covert mission to guide Harry Potter through the challenges of the Triwizard Tournament.
The Magical Mixture, while a minor object, plays a subtle but important role in Harry Potter and the Goblet of Fire.
The term “Magical Mixture” is generic and is used on only one occasion in the novels. This ambiguity may be intentional, contributing to the mysterious and slightly chaotic collection of objects that the real Alastor Moody was known to possess, a trait his impostor, Barty Crouch Jr., effectively mimicked.