"That was a fine explanation of Levitation Theory you gave in class Miss Granger," he said warmly. "I look forward to reading your essay on the subject." He paused as they stood silently in front of him.

"May I, uh, assist you in some way?" he said.

Hermione looked around behind her to be sure that all the other students had gone. "Um, Professor, we were wondering if maybe you would ... or, actually, if you still know ... erm, if you can ..."

"Miss Granger," he said with genuine kindness, "Don't be shy. I am here to help you learn as much as I can during my appointment this year. You are all welcome in my office at any time if you need extra help with your assignments."

"Well, Professor ..." she could think of no other way than to just blurt it out. "We were wondering if you still possess your ancestors' knowledge of digitomancy, and if you would teach it to us for possible use in the coming war against the forces of the Dark Lord." Professor Carstairs looked stunned. Apparently that was the last thing he had expected to hear from a student.

"How can you possibly know about that?" he asked in disbelief. "That technique has been a closely guarded secret in my family for many centuries. Salazar Slytherin, who had a great gift for digitomancy, forced my ancestor to teach him the technique nearly a thousand years ago. But Slytherin selfishly took that information to his grave without ever teaching it to his followers or to his own sons. Where could you three possibly have heard about it?"

"Speculum Occultum," said Hermione simply.

Carstairs looked at her with renewed respect.

"And you figured out how to read it on your own, did you? I guess we should have destroyed that last copy. I knew it was held by the Hogwarts library, but having been a scholar all my life, I couldn't bring myself to destroy the last surviving copy of such an ancient work, especially one which documented some of the early history of my family." He sighed heavily.

The Bloody Baron, whose real name was Baron Rudolph Hohenzollern von Greifswald of Schleswig-Holstein, was now known to his students as "Baron Greifswald." He appeared to be about 60 years old (at the time of his death), and, like Mad-Eye Moody, he showed the marks of many battles. His face was pockmarked and scarred, several of his teeth were missing, and he wore a patch over one eye. Harry had never known much about him, but it turns out that the Baron had been quite a prominent sorcerer in his day, and had triumphed over many dark wizards by using their own techniques against them. "The best defense is always a strong attack," he croaked, and gave many fascinating examples of his own cunning in launching brutal and merciless pre-emptive strikes and surprise attacks against his enemies. Harry sometimes failed to grasp the defensive aspects of these exploits, since it was clear that the Baron's enemies had to be ever on the defense against him.

Another of Harry's favorite classes in his sixth year was Spellogenesis, the invention of new and original spells, which was taught by Professor McGonagle. It was quite as complex as Transfiguration, the other class McGonagle taught, and Harry was proving to be even more adept and creative at it than Hermione. Ron, however, was having a miserable time. None of the spells he tried to create worked, and many of them fizzled in embarrassing ways, such as his "bottomless butterbeer glass" which instead poured out rancid carrot juice.

"Spellogenesis was your twin brothers' best subject by far, Mr. Weasley," said McGonagle in exasperation. "Surely if those two boys can master it then you can ... although I worry that they are not putting their skills to uses that the faculty would approve of."

McGonagle was referring, of course, to Fred and George's highly successful joke shop in Hogsmead, Weasley's Wizarding Wheezes, where they were developing and selling a wide variety of original and often somewhat dangerous potions and devices that they thought would be amusing. Some of the faculty were concerned about the renewed level of chaos that might then be injected into Hogwarts, but Professor Dumbledore seemed merely amused and completely unworried; Harry even detected a glint of pride in Dumbledore's twinkling eye.

Harry, as part of his quest for better weaponry against the forces of Lord Voldemort, had been going back and forth between Baron Greifswald and Professor McGonagle, getting ideas for nasty new spells from the Baron and then investigating their feasibility with McGonagle. Professor McGonagle recommended strongly that for every new spell someone invented, they should also create the corresponding countercurse. This was necessary if they were to practice any of them in class on people or things that they wished not to permanently affect, destroy, mutilate, mutate, or otherwise render awkward.

The Baron, however, had a different opinion: "Boy, if you're going to be doing battle with your new spells and curses, don't create any methods of blocking or countering them! If you happen to be fighting a good legillimens, he will snatch those counter-techniques right out of your head and apply them against you before you can say Frederick the Great's your uncle.' Better to leave your opponent with no easy defense."

Harry had been working secretly on a new spell that he thought might surprise Voldemort's Deatheaters enough to prove effective. He had remembered a term paper that Hermione had written a couple of years ago, "Why Muggles Need Electricity," and this in turn had reminded him that the wizarding world generally did not utilize electricity in any way. All lighting and cooking at Hogwarts, for instance, was accomplished by fire, the magician's ancient source of power. So, reasoned Harry, if he could come up with some kind of spell involving the projection of an electrical charge, this might be so foreign to most wizards that they would be at a loss for ways to block or counter it. He decided that his incantation for this spell would be Fulguritim!, from the Latin expression for being struck by lightening.

That was the easy part, however; he still had to create a complex mental formula, to be carefully memorized, that would result in the desired effect, and he was having no luck. Despite having followed all of the recommended procedures in the spellogenesis textbook, he was still unable to generate a single spark with his wand. He was determined, however, to succeed, and to do so without asking Hermione for help. He wanted to create this one by himself. He figured that the spell probably just needed to be made stronger, so he altered the mental formula repeatedly, though without much apparent effect.

Harry's desire for secrecy had been increasing ever since he had gained full access to the Restricted Section of the library, as part of his Independent Study group with Ron and Hermione. Lately he had been visiting the library alone whenever he could, and had been reading more and more about the Dark Arts. Things he never would have considered learning now seemed ever more pertinent and necessary if he were to survive the coming battles. Techniques and spells so horrible that he would ordinarily have been repulsed by them now appeared worth considering. He lay awake on many nights, turning them over and over in his mind.

One clear and sunny afternoon, while reading over a book on the use of reptiles in spellcasting, it suddenly occurred to Harry that since Voldemort was the last surviving heir of Salazar Slytherin, it might be worthwhile to study all that was known about the life and death of that ancient wizard and Hogwarts co-founder.

Beginning with Hogwarts, A History, he began tracking references backward in time as he had done when he was researching digitomancy. Ultimately this trail of references led him to Salazar Slytherin, Necromancer of York (1629) by Clothilda Pashley. Harry spent all afternoon studying it. Near the end he found this passage:

"Couringius and Guibertus, Disciples of the Snake, both confess that they had witnessed the death of Salazar Slytherin in the year 1014, at the venerable age of one hundred and thirty-seven years, this being twenty-one years following his departure in anger from Hogwarts College. It is said by those learned writers that Slytherin had many years earlier prepared for himself a resting place which was known only to his followers. He was carried in procession back to that secret place, which they called the Sepulcrum Subserpens, and there was he interred."

Harry thought about this for a long time. The Sepulcrum Subserpens translated as the "Crypt Beneath the Serpent," according to the Latin dictionary he had found. Apparently no one other than Slytherin's followers, all of them now long dead, knew where this burial place was located. Perhaps there was a carved serpent on a rock face in the mountains somewhere, standing over the grave of Salazar Slytherin. Then again, if Slytherin had prepared his own burial place for himself many years in advance, it could have been prepared while he was teaching at Hogwarts, or even while Hogwarts Castle itself was still under construction. After all, he was able to secretly prepare ...

Harry was suddenly dumbstruck with a revelation. Of course no one had ever known where the secret burial place was! It was part of an even bigger secret, the Chamber of Secrets itself! Subserpens, beneath the serpent, must refer to ...

It was late, and the sun had long since set, leaving Harry working only by dim candlelight. Everyone had already left the library to go off to bed, including Ron and Hermione. Harry was alone, with no one to tell. He stood up, thinking furiously. A plan took shape in his mind, a plan he would have to carry out by himself with no help from Ron or Hermione.

He strode out of the library, as if pulled along by an invisible hand, and made his way through the corridors and up the various stairways to Moaning Myrtle's lavatory. He hardly noticed Myrtle, who greeted him sweetly but then dived into a toilet, miffed at his failure to even acknowledge her.

Harry tapped the faucet marked with the small snake, and hissed "Open up!" in parseltongue. As it had done once before, the pipes and stone sinks spun and sank to reveal the large pipe leading down to the Chamber of Secrets. Harry stepped into the black hole, slid down the long vertical passageway, and was soon clambering his way over mold-covered fallen rocks, with only the light of his wand to illuminate the eerie surroundings. Eventually he was standing once again in the gloomy hall of towering stone pillars entwined with carved snakes, where he had fought and killed the giant basilisk four years earlier. Facing him was the enormous carved stone statue of Salazar Slytherin, from out of the mouth of which had issued the basilisk when it had been summoned forth by the ghostly reflection of Tom Riddle.

Quiet hung in the damp air like a leaden weight. Only the faint drip of water echoing somewhere back in the dark caverns around him reached his ears, and Harry felt very much alone and small. He looked around nervously, then returned his gaze to the stone face. "That's where the basilisk came out," he thought to himself, "so I guess I'd better get on with it."

Screwing up his courage and taking a deep breath, he climbed up the statue and crawled into the black mouth hole. The walls of the opening were slimy, perhaps a residue left years ago by the basilisk. He crawled along until dropping out into an enormous open chamber. His wand light barely reached the stalactite-covered ceiling high above and the moldy walls streaked with dark rivulets of water. Littered about were countless huge snakeskins which had been shed by the basilisk-this was clearly where he had lived for centuries. The rotting musky smell must have been stronger when the creature was alive, but had since been slowly fading.

Well, thought Harry, this had been the lair of the great serpent of Slytherin, so the burial chamber must be below it somewhere. He began searching all about, but found nothing. In frustration he called out a few incantations that echoed across the great chamber, but nothing happened. Then, on an impulse, he called out Dissendium! in parseltongue, and almost fell into a stone stairwell that suddenly opened in the floor in front of him.

Harry descended the stairway into a smaller chamber. At the foot of the stairs lay a huge stone sarcophagus with what at first appeared to be a body atop the lid, but the body proved to be a full-size image carved in stone depicting Salazar Slytherin lying on his back, partially clad in armor, and with a long and straight-bladed two-handed sword at his side. The flat-nosed snakish features of his face bore an uncanny resemblance to the features of Lord Voldemort-there was no doubt that they were related. The sightless stone eyes stared at the ceiling with a look of aristocratic annoyance that anything so pedestrian as death could have overtaken him.

Harry steeled himself against what he was about to see, then gave a mighty heave and pushed off the lid of the sarcophagus to reveal the body of Salazar Slytherin inside. Actually, he doesn't look too bad, thought Harry. The skin was taught and slightly transparent, the empty eye sockets were black, and the enormous mane of ash-gray hair and beard were still perfectly intact. His bony arms were crossed over his chest like those of a Pharaoh, and he wore a dark purple cloak decorated with silver stars. A signet ring with an engraved emerald depicting a snake was on his finger. The faint odor of decay filled the air. Harry felt a wave of reverence to be looking upon the actual thousand-year-old corpse of one of the founders of Hogwarts.