The fourth installment of the Harry Potter series, Harry Potter and the Goblet of Fire, opens as a mysterious force mysteriously chooses Harry to compete in a dangerous tournament against three other contenders. But the question immediately arises—who put his name in the Goblet of Fire?
At first, the Hogwarts staff and other teachers were sure that it was a joke and that no one had actually put Harry’s name in the Goblet. Dumbledore even went so far as to accuse Harry of entering his own name, though he quickly retracted this accusation and began to investigate further.
As it turns out, the one responsible for placing Harry’s name in the Goblet was an evil wizard named Bartemius Crouch, Jr. Crouch, Jr. was impersonating Alastor "Mad-Eye" Moody, a teacher at Hogwarts, and using Moody’s legendary magical ability at Transformation to take his place and manipulate the tournament rules.
Crouch, Jr. was a former Death Eater, one of Voldemort’s followers, and he wanted Harry to compete in the tournament to prove the strength of Voldemort’s dark magic. By placing Harry’s name in the Goblet of Fire, Crouch Jr. was able to circumvent the magical safeguards and rules blocking underage competitors.
As Dumbledore pointed out, Crouch Jr. had a special knowledge of dark magic, something regular wizards and witches were unfamiliar with. He was able to use a complex set of spells, relying upon both traditional and dark magic, to alter the magical boundaries of the Triwizard Tournament, allowing Harry’s name to be drawn from the Goblet.
It was revealed that Crouch Jr.’s mother had helped him to place the name in the Goblet, as a means of revenge against his father for imprisoning her. Crouch Sr. was a Minister of Magic and had no tolerance for dark magic users, so his son had been more than willing to take advantage of this opportunity to get back at him.
In the end, Crouch Jr. was defeated and sent to the wizard prison Azkaban for his misdeeds. It was a reminder of the power of dark magic and a warning to all Hogwarts students of the dangers of meddling in it and the great cost of challenging the laws of magic.
So, the villain behind placing Harry’s name in the Goblet of Fire was Bartemius Crouch, Jr., an ex-Death Eater with a grudge against his father and a taste for dark magic. His actions were a reminder of how powerful dark magic can be and a warning to stay away from it and its consequences.