The Big Problem With Harry Potter And The Goblet Of Fire's Triwizard Tournament
After three installments in the Harry Potter saga that followed fairly similar structures, J.K. Rowling changed up her formula for the fourth book, Harry Potter and the Goblet of Fire. In this installment, there was no quidditch at all. Instead, we got the Triwizard Tournament, an event designed to pit champions from three schools of magic against one another. The wrinkle at the center of the book is Harry's (Daniel Radcliffe) involvement in the tournament, which means that there are two champions from Hogwarts, the other being Cedric Diggory (Robert Pattinson).
Although the tournament provides a compelling dramatic framework to hang the story around, there are some who have noticed a few flaws in logic — and even a plot hole — in the way that it unfolds.
In the tournament's second task, Cedric and Harry, along with Fleur Delacour (Clémence Poésy) and Viktor Krum (Stanislav Yanevski), the champions from Beauxbatons and Durmstrang, respectively, are forced to dive into the lake near Hogwarts in order to rescue someone each of them cares about from the lake's murky depths. And here's where the problems start.
How Viktor Krum's solution in Goblet of Fire violates the rules of magic
Ahead of that watery task, each champion is advised that they will need to find a way to breathe underwater for an extended period of time. The book takes pains to show Harry struggling to find a way to do this. In the book, he's ultimately bailed out in the eleventh hour by Dobby, who shows up and offers him gillyweed, a magical plant that allows him to temporarily adopt the qualities of a fish.
While Harry's underwater breathing tool works perfectly, it's actually not his gillyweed that's the problem. Digory and Delacour elect to use a charm that wraps an air bubble around their heads, and Krum decides to turn his head into the head of a shark. It's that shark head that winds up being the problem, as it violates already established rules around transfiguration. In this case, it seems that J.K. Rowling may have inadvertently contradicted herself.
In Goblet of Fire, Viktor Krum probably would have eaten Hermione instead of saving her
Krum's transformation into an animal may not seem unusual in the world of Harry Potter. After all, we know that characters like Sirius Black and Peter Pettigrew are capable of transforming themselves into animals, and they do so fairly regularly. What Krum is doing is different, though. He's using transfiguration to turn part of his body into a shark, but that status isn't a permanent condition the way becoming an animagus is (via Wizarding World). Once Krum returns to his human form, he'll presumably stay that way moving forward.
Given the fact that Krum is using transfiguration — and considering the rules around transfiguration that were established in Quidditch Through the Ages – Krum's actions in Goblet of Fire don't make a ton of sense. As Quidditch Through the Ages establishes, transfiguring yourself into an animal means losing the human part of your brain. As a result, Krum would be much more likely to eat Hermione, instead of rescuing her, when he travels into the lake outside Hogwarts.
What's more, Krum would have needed help from another witch or wizard in order to de-shark himself. And thus, Krum's use of magic is a clear contradiction of the rules Rowling established for her magical universe, even if it is a relatively minor infraction.