Blocking the Trace

To block the Trace, he first had to understand what it was.

The Trace was a wide-area tracking magical mark that the Ministry of Magic placed on every underage wizard under seventeen.

It was used to monitor young wizards and prevent them from improperly using magic outside school.

It had already been imprinted within Li Wei on his first day at Hogwarts, when he crossed the Black Lake.

Li Wei recalled what he had once read about the Trace in a book:

[The Trace only binds to underage wizards. When they pass their seventeenth birthday, the Trace automatically becomes invalid.]

The first method Li Wei thought of was to fool the Trace into believing that he was already eighteen.

[The Trace detects surrounding magical fluctuations and magical activity, then alerts the Improper Use of Magic Office.]

[It only reports the location, time, and type of magic. It cannot tell who cast the spell.]

The second method Li Wei thought of was to exploit this feature of the Trace and simulate the presence of an adult wizard beside him.

He would make the Trace believe that an adult wizard was casting the spells, rather than Li Wei himself.

"Two mechanisms, two countermeasures. Both methods need to be tested!"

Sitting cross-legged on the floor, Li Wei pondered his options.

The first thing that came to mind was Aging Potion. A single drop of this potion could age someone by one year.

During the Triwizard Tournament in the fourth year, the Weasley Twins had tried to use Aging Potion to fool the Goblet of Fire and enter their names.

But Li Wei was not foolish enough to believe that Aging Potion could deceive the Trace.

Aging Potion merely increased a person's apparent age.

In reality, neither their bone age nor the marks left