A/N: Here we see the start of Harry's deeper magical studies, and my copious usage of Google Translate for spell names :)
[Hogwarts Library, End of Harry's Third Year]
Harry sighed. He had been searching for a way to infuse runes into his spells, since Hermione had seemed so enthused over that branch of magic. Borrowing her notes had let him quickly figure out the basics, but advanced uses of runes seemed to not be in any books he had searched thus far. Ron had finally managed to convince Hermione to relax and play chess, and last he had checked, his two best friends were locked in an intense series of successive matches. Trust Hermione to turn a pickup game of chess into an endeavor.
The book he had picked up was on Norse runes, and should have been intuitive to him according to Hermione, thanks to the ease with which he had picked up the Futhark runes from her notes, but the runes seemed to spend most of his study time by swimming on the page and making zero sense overall. He had wanted to use Norse runes thanks to the Nordic tendency of high-powered runic spell combinations, especially when one investigated Norse mythology. Imbuing a hammer with the power to call down lightning bolts was possibly one of the most common uses of high-end Nordic runic enchanting, but Harry wanted to explore the possibility of imbuing elemental spells with runic properties.
He had found an old book on his study table earlier, one that had pointed him in the direction of high end uses of rune-based enchantment, but Hermione could not possibly have left it there. He didn't question it much, assuming it to be a quirk of the library. Perhaps it could help students with their studies? At any rate, he had to continue his studies, Nordic runes were his best bet, being new enough that he could read them without a translation book, but old enough that they had a significant amount of power behind every rune.
Runes built up power based on how often they were used, an interesting theory that he had found in the old rune book. It was the reason that runic alphabets crafted in the last few hundred years had very little power behind them, unless they were the creation of an incredibly powerful wizard or witch that made up for the lack of use with their own inherent magical strength. Runic languages held the most power, as did ancient magical languages, due to the pure strength lent to every letter or phrase over hundreds to thousands of years of use. Latin fell into an interesting hole. It was old enough that Latin words had power, but new enough that individual letters had not gained significant strength. That led to many modern countries using Latin origin spells, even if they were translated into their everyday language.
Older civilizations however, had no need for the "Latin crutch", so to speak. Their ancient languages were steeped in enough history and magical power that they had no need or desire to switch languages or use translations. An Indian mage had no use for Incendio, they used AgnibaN. The sheer power that most ancient Indian, Chinese, Egyptian and Mesopotamian spells packed behind them were staggering. It was little wonder that Curse Breakers strong, brave and clever enough to venture into ancient Egyptian tombs were so sought after. Even after millennia, curses from the most ancient cultures still had weight and could kill an entire research team if not worked around very carefully.
This fed into Harry's desire for Nordic runes, young enough to learn quickly, old enough to pack some punch. Hopefully he would be able to figure them out quickly, he still had to master the Aguamenti water conjuration spell as well as the Glacius freezing spell in order to have some material to infuse the runes into.
She watched from behind a bookcase. The Potter boy had come yet again, without his friends, yet again. He seemed to be feverishly searching for information. Some of those tomes hadn't been opened in decades, let alone years. Not since the last powerful and curious wizard to have walked the halls of Hogwarts.
She…did not exactly like the Boy-Who-Lived. He was tolerable. He treated books with the respect they deserved, even if he didn't quite treat his homework with the same. The boy wasn't quietly studious, like the Ravenclaws, or hard working like the Hufflepuffs, but she would be lying if she said he didn't apply himself to his studies. And yet, he had made friends with Hermione Granger, quite possibly the closest to her own heart in regards to books.
She had seen his studies focused on runic enchanting for the past few days and had slipped him a primer on higher end runic languages and enchantments, wanting to see how he assimilated the information. Pince could practically see the boy's frustration with his chosen runic alphabet. She sniffed primly. Nordic runes were always a little too straightforward for her. The elegance of Arabic runes or the sheer deadly grace of Egyptian runes were more her style.
Perhaps the boy needed a nudge in a different direction. She resolved to leave a book on Egyptian runes on his study desk tomorrow and see how he progressed from there. And perhaps, a primer on higher elemental conjuration. She had seen his initial attempts to learn Aguamenti, and they had been rather uninspired. If he was headed in the direction she thought, that of infusing runic effects into elemental conjurations, he would need a significant amount of help. Third year texts simply wouldn't cover knowledge that esoteric. Nor would Seventh year texts, for that matter. Luckily, the Hogwarts library had tomes for more than just the basic magical educations, and covered many texts suited for wizards and witches starting their Apprenticeships.
Harry rubbed his forehead. Hermione and Ron were now locked in a protracted struggle in the common room involving chess, and his own studies seemed to be locked up as well. Nordic runes were impossible to decipher, even with modern translations. They just didn't click for him.
He was starting to think that the Library was sentient, since it seemed to know exactly what he was having problems with and how to help, since he had walked in that morning to see two thin but ancient handbooks. One that gave a variety of exercises on how to improve and strengthen his elemental casting, which would make his water and freezing spells far more effective. The second was a guide on ancient Egyptian runes. They were not completely separated from hieroglyphics but had a magic of their own.
Thanks to the inexhaustible efforts of modern Curse Breakers, the majority of ancient Egyptian runes were known and could be utilized, even if students had to build in numerous safeguards and ways to leech power off of the rune effects, thanks to the absurd amount of power contained in even a simple phrase such as "conjure water".
For example, a basic Nordic cluster that existed to conjure water would often create either a low powered blast or a small stream of water. Depending on how it was tuned by secondary clusters and phrases, you could put the runic structure on a metal tube and create a serviceable but inefficient shower. Or turn it into a low powered water jet to use as a gardening tool.
The same basic cluster written in ancient Egyptian, however, would do nothing less than emit a highly attenuated cascade of water, thin enough to cut through rock or thick enough to bowl over a fully grown wizard. The cluster would have to have numerous secondary clusters built in to regulate the flow of water but would be ultimately useful for nothing less than an industrial level water cutter or cleaner.
This information was incredibly helpful, and he barely needed to consult a translation book, the Egyptian runes and their meanings seemed to practically jump into his brain. His main worry had been augmenting his attacks with a quickly drawn rune, and it seemed that ancient Egyptian runes were almost uniquely suited for exactly that. A traced strength rune would imbue the next spell with almost triple the force as he could regularly output, and he was learning that many Curse Breakers or Runic Enchanters used a secondary focus such as a metal or stone rod to trace their runes, allowing for them to let loose a constant barrage of spells while continuously strengthening or otherwise modifying them with runes.
Harry had also spent a significant amount of time studying anything he could on how Voldemort had fought before his downfall, and the majority of it seemed to have been Dark magic cast with frightening amounts of power, or just straight up Unforgiveable curses. The only times he had relied on anything other than curses had been whenever Voldemort had faced up with the Headmaster. Then the duels they conducted seemed to take a level in power in skill. Battle Transfiguration was the Headmaster's forte, and Voldemort seemed to have his niche in Dark curses and fire conjuration, as well as serpents worked into a large quantity of his spells.
Neither of the two seemed to use runes in their spells, but Harry figured that perhaps Dumbledore didn't have any need to augment his spells, since they were cast with a terrifying power of their own, especially on top of his Battle Transfiguration. And Voldemort appeared to prefer brute force spells, and had enough inherent power to back up the destructive curses he favored.
Several Dark elemental curses seemed of interest to Harry, but their initial or set up costs were either too high, or they enacted a terrible toll on the mental health, physical health, or magic of the caster. Fiendfyre, possibly the most famous Dark elemental curse, was nearly always fatal to the caster, unless they held enough willpower to vanquish the living flames, and the only way to know if you had that willpower was to cast it. And there was no such thing as casting a little bit of Fiendfyre for practice, since it would feed itself on the magic of the caster even if there was no other magic around for it to feed on otherwise. Tenebris caligo was the Dark freezing spell, and it enacted a toll of permanently shaving one day off of the caster's life for every attempt of the spell. So even practicing the spell was harmful to the life of the caster.
Harry figured it would be simpler to rely on the existing normal elemental spells, instead of heading down the path of harmful to cast magic. At least magical exhaustion from over casting spells was preferable to chopping days off of his lifespan. And using runes to augment the power of his spells would neatly make up for his immature magical strength and lower amount of magic in comparison to Voldemort and his Death Eaters.