The principles behind Marauder's Map are extremely complex. Although it doesn't have the wide search range of Muggle's radar, it can accurately locate any target within its range.
First, it displays names by using soul-marking magic to accurately identify the magical mark of each individual.
The reason the SAS Tactical Dagger can be identified as Lucy is because Vincent created a recognizable magical mark after naming it.
Next, the map's ability to cover any known corner of the castle is due to the spatial grid distribution used by the creators when they drew it.
This was an extremely large project. Without the Animagus Transfiguration and without the help of the School Board Member's authority, it would have been impossible to complete the drawing during Hogwarts' seven years of schooling.
Then comes penetrating invisibility and disguise, which utilizes anti-invisibility spells and Transfiguration detection that are even more advanced than soul-marking magic.
The Black Family possessed countless spellbooks, Sirius Black only managed to find these two spells by sheer luck.
Finally, by combining the Revealing Charm and the Mantra of Revealing Traces, one can achieve the effect of real-time display and continuous tracking.
To prevent a certain annoying person from finding out, the map's creators specifically set up four separate ideas, and also added anti-crack spells and spell locks.
Once that annoying person utters the password, even if it's the correct one, you'll only get false information, or even be collectively humiliated and verbally abused.
Vincent listened with a furrowed brow to Sirius Black and Lupin's explanation of the principles.
To be able to apply various kinds of magic without conflict to a map the size of a parchment, and still function normally twenty years later, requires not only superb magical skills but also a certain amount of luck.
Vincent relaxed his brow slightly. "If I may ask, how many times did you fail back then?"
Lupin took a sip of whiskey and raised his hand to show three fingers.
"Three times?"
Sirius Black shook his head.
"Uh... 30 times?"
Lupin slowly put down his glass. "It took us a whole year, a total of 300 attempts, to successfully create a single map."
Vincent's vision went black.
Although the Forbidden Forest and Black Lake have much simpler spatial structures than castles, their combined floor area is several times larger than that of castles.
A year has passed, the Triwizard Tournament is long over, and even the most foolish Death Eaters who went into hiding should have completed Voldemort's mission and run away by now.
However, after more than a decade, the success rate of creating Marauder's Map has certainly improved.
However, this is where Sirius Black and Lupin's difficulty lies. Because creating the Marauder's Map was too difficult back then, they chose to divide the work, with each of the four of them responsible for one aspect.
Sirius Black was in charge of the soul-marking magic, Lupin was in charge of revealing and continuous tracking, James Potter was in charge of anti-invisibility spells and Transfiguration identification, Peter Pettigrew was in charge of mapping.
"Shit!" Vincent couldn't help but curse.
He and Hermione overlooked the possibility that Peter Pettigrew was involved in creating the map. However, if he was only responsible for drawing it, he probably wouldn't know what magic the map used or what principles enabled its location tracking.
As long as it doesn't exploit low-level vulnerabilities, there are still ways to find the hidden Death Eaters.
Judging from their expressions, it's highly unlikely that Peter Pettigrew didn't know.
"Please don't tell me he knows..."
Sirius Black suddenly raised the half-full bottle of whiskey and drank it down.
Lupin nodded at Vincent with a wry smile.
That's it, Marauder's Map is completely unusable unless a new map is created using other magic and principles.
Vincent stared quietly at the glass in front of him, which was almost empty of whiskey.
Moody's Magic Eye can see through the disguises of Invisibility Cloak and Polyjuice Potion, which is quite similar to anti-invisibility spells and Transfiguration detection.
Since even he didn't find anything, we can rule out the possibility that the Death Eaters used invisibility or Transfiguration.
Marauder's Map's soul detection magic, which accurately identifies magical imprints, is indeed powerful, it cannot identify incomplete souls like Voldemort's, or magically modified wizards like Quirrell.
It seems the only way to find the Death Eaters is to examine them one by one.
"Sigh... this is so hard..."
Sirius Black got up and walked over to the bar, carefully examining the wide variety of liquors on the shelf. "It's really difficult to find something that can fool Mr. Moody's magic eye."
He picked up a bottle of grass-green absinthe from Spain and gently raised it towards Lupin. "Remus, would you like to try this?"
Why drink grass-green absinthe instead of golden whiskey?
Lupin shook his head and retorted, "Don't you hate green the most? Doesn't green remind you of Slytherin?"
Sirius Black came back with the wine. "Come on, it's just drinking. Why should I overcomplicate things?"
Lupin downed his whiskey in one gulp. "Okay, I was just saying."
"You're overcomplicating things..." Vincent suddenly stood up, startling Sirius Black so much that he almost bumped into him.
"Hey! Be careful, this wine isn't common in Britain. I've always wanted to try it."
Vincent didn't react at all, and kept muttering things like "complicate things".
Sirius Black, rather helplessly, walked around to his seat and returned to his own.
He took a new glass and poured some absinthe for himself and Lupin.
Just as the two were about to clink glasses and have a drink, Vincent suddenly turned his head and looked over.
"I've got it!"
The sudden shout startled both of them, causing a few drops of grass-green liquor to spill onto the bar.
"Hey! You're doing this on purpose, aren't you?"
"I'm sorry." Vincent sat back down, his voice trembling with emotion. "I have a way to find that Death Eaters."
Sirius Black and Lupin quickly put down their glasses.
"What method is it?"
Vincent gave a wicked smile. "If that Death Eaters is hiding in the school, he'll be extra careful, watching his words and actions constantly, afraid of being exposed by accident, right?"
After receiving nods from the two, he continued, "So the school will be safe until the Second Task, right?"
Sirius Black and Lupin exchanged a glance, understanding his plan.
Rather than risk alerting the enemy by screening and confirming each one individually, it's better to wait patiently for the Second Task to arrive.
Unless Voldemort's mission has already been completed, they will definitely sabotage the match before it even begins.
So, as long as we are prepared to wait patiently, we can find the person without going to great lengths.
Vincent reached for the absinthe in front of Sirius Black and poured himself a drink. "While we wait for the Second Task, we can use that time to create a new Marauder's Map."
He raised his glass to the two men, saying, "If we're lucky, we might be able to find the person ahead of time."
With a "ding," the undiluted grass-green liquor instantly made the three of them frown.
Soon, their facial features were all tightly furrowed.
"Shit! What is this stuff? It tastes awful!"
"Isn't this wine supposed to be diluted with water before drinking?"
"I feel like my tongue no longer belongs to me."