Horcruxes

According to the cross-reference between the original Harry Potter books and Isaac's prophecies.

The first Horcrux Voldemort created should have been Tom Riddle's Diary, the one Harry dealt with in his second year.

Voldemort had created the diary Horcrux in his fifth year, when he was sixteen.

After graduating, Voldemort had entrusted the diary to his follower, Lucius Malfoy.

That also meant the diary should still be at Malfoy Manor.

Likewise, Isaac had not seen the diary in his prophecies. Clearly, as one of the pure-blood families, Malfoy Manor possessed something that blocked prophetic observation.

Perhaps it was some alchemical artifact, perhaps Malfoy Manor's magical defenses. In any case, Malfoy Manor was a black hole for prophecy magic.

But.

Isaac had to say that Malfoy Manor being excellent did not mean Lucius Malfoy was excellent too.

As long as Lucius Malfoy stepped out of Malfoy Manor, Isaac could make prophecies about him.

Thus, in Isaac's prophecies, Lucius Malfoy was like an office worker clocking in and out—Isaac could see him whenever he left home. But once he returned, it was as though he had moved into a black hole.

Voldemort's diary could not currently be observed through Isaac's prophecies precisely because it was stored at Malfoy Manor.

The second Horcrux Voldemort created had also been made when he was sixteen.

At the end of his fifth year, sixteen-year-old Tom had gone to Riddle House in Little Hangleton to take revenge on the Muggle father who had abandoned his mother, murdering his own father.

He had not only murdered his father, but also his grandparents—a family of three.

He had turned the ring passed down through generations of the Gaunt Family into his second Horcrux and hidden it in the Gaunt Shack.

Though this Horcrux had been hidden in the Gaunt Shack, Isaac could observe its existence through prophecy.

Isaac guessed that the reason he could not see Malfoy Manor but could see the Gaunt Shack might be that the Gaunt Shack had fallen into disrepair over the years, and the protective spells used to block prophecy and divination had failed.

Furthermore, the gem on Gaunt Ring was the Resurrection Stone, one of the Deathly Hallows.

That thing was practically a hard counter against Dumbledore and Snape.

Next, at the age of nineteen, Voldemort had made his third Horcrux from Slytherin's Locket, hiding it in a seaside cave in Britain.

Later, Slytherin's Locket had been swapped out by Regulus Black and was now hidden in the Black Family's ancestral home.

Because the Black ancestral home was maintained by House-elves, it could not be observed either, just like Malfoy Manor.

Then came the fourth Horcrux, made from Helga Hufflepuff's Cup. Since it was currently stored in a Gringotts vault, Isaac could not observe it through prophecy either.

As for Gringotts, Isaac had actually used prophecy to secretly observe it long ago. He remembered that after the attempt had failed, Grindelwald had laughed at him mercilessly.

Isaac suspected that Grindelwald must have done the same thing before. Otherwise, why had he laughed so happily?

He, Isaac Waldore, the person in the Wizarding World most like Grindelwald, merely wanted to take a look at a wizard bank's vaults. So what?

Sneaking a peek was not against the law, was it?

The fifth Horcrux was the Diadem of Rowena Ravenclaw, which Voldemort had made when he was around twenty. It was currently sitting in Hogwarts's Room of Requirement.

As for the living Horcrux Voldemort made from Nagini in the original books, there was not even a trace of it yet.

Poor Tom had only just been brought back from the forests of Albania by Quirrell, only to have a centenarian block his door. Even if he wanted to make a Horcrux, he did not have the ability.

Lastly came the Horcrux Voldemort had created by accident: the Wizarding World's The Boy Who Lived—Harry Potter.

Isaac drew symbols only he could understand, then took out his wand and tapped the parchment.

The parchment promptly turned to ash.

Voldemort had created six Horcruxes, but Isaac could only foresee half of them, and that half had to include Harry Potter, the living Horcrux.

If Harry was excluded, then there were only the Resurrection Stone ring in the Gaunt Shack and Ravenclaw's Diadem in Hogwarts's Room of Requirement.

Why did Isaac keep the locations of the other Horcruxes secret from Dumbledore?

The main reason was still the Resurrection Stone in the Gaunt Shack.

He truly did not dare let Dumbledore know about that thing.

Isaac knew very well that Voldemort had cast a powerful curse on that ring, one even Dumbledore could not avoid.

Voldemort had torn apart his soul to create Horcruxes, turning himself into a monster, but it had not been without benefits.

The benefit he gained was that his talent for Dark Magic had been greatly enhanced.

At such a young age, he had entered the realm of a Dark Magic master and charged recklessly a considerable distance down that path.

He had achieved accomplishments far beyond those of his predecessors.

Voldemort was practically Grindelwald's opposite—despite his astonishing talent for Dark Magic, Grindelwald had not studied Dark Magic alone.

Like Dumbledore, Grindelwald had followed the most orthodox path available to wizards: the path of a traditional magic master.

He had held on to his true self, refused to be influenced by magic, and become a master of the Wizarding World through sheer strength.

Voldemort, meanwhile, had essentially taken a shortcut through Dark Magic. By creating Horcruxes, he had allowed Dark Magic to thoroughly taint his soul.

This had terrifyingly enhanced his talent in Dark Magic, but it had also weakened his sanity and made Dark Magic exclusive within him.

After creating Horcruxes, whatever magic Voldemort invented or used carried the distinct flavor of Dark Magic.

As a traditional magic master, Dumbledore was stronger than Voldemort because he had more ways to resolve any given matter or deal with any particular person.

Voldemort, on the other hand, could only use Dark Magic to solve problems.

That also meant Voldemort's Curses were on the same level as Dumbledore.

Voldemort's curse might not kill Dumbledore immediately, but resolving it would not be simple either.

And the Resurrection Stone's allure to Dumbledore was fatal.

Isaac did not think he could stop a crazed Dumbledore. What could a little Grindelwald like him possibly do?

The real Grindelwald would have to step in.

But then another problem arose. Grindelwald was still imprisoned in Nurmengard—if he did not get out, who could stop Dumbledore?

For the sake of caution, Isaac decided to conceal the existence of the other Horcruxes for a while longer.

Once he had gotten acquainted with Hogwarts's other professors, he would directly form a Horcrux Purge Squad and raid Voldemort's old haunts together.

If nothing unexpected happened, Isaac would see Hogwarts's Heads of House in the Great Hall tomorrow.

Although Isaac was already very familiar with these professors who taught him in his Prophetic Vision, the professors did not know him yet.

Old Dumbledore really was something. Did he not understand that once a surprise was discovered in advance by a Seer, whether he revealed the details or not, the Seer would definitely know?