Ideas: end of 5th year, sirius death,wizarding space, dark harry, necromancy maybe?, weasley bashing (ron + ginny), hermione bashing, spell creation, smart harry.
Harry soaks in his bitter anger as Weasley and Granger prattle on and on. Miss Know-It-All keeps sending wary glances towards him as if she can tell he's only just barely keeping control over his magic. Meanwhile, Weasley is stuffing his face rapidly and arguing with Granger about something presumably insignificant and meaningless. Standing, Harry mumbles excuses about being tired and leaves the hall.
He is so sick and tired of those two idiots clinging to him and pretending to care. They only want to be friends with the boy who lived and not Harry Potter. This was made blatantly clear with the ginger's constant jealousy of Harry's 'fame', and the pair's constant bragging about being his friend when they thought he couldn't hear. Admittedly, at first he didn't know, however, he has always been sneaky, especially with who he was 'raised' by, he wouldn't have survived if he hadn't learned to be somewhat sly and resourceful.
flashback to first year
When he met Weasley on the train, he was just glad to have made friends with someone, despite how uncomfortable he felt when the red-head commented about his scar and how he was friends with 'The Harry Potter'. He finally had a friend that Dudley couldn't scare away. Granger seemed like a bit of a bully with her pretentious attitude, so he was glad that his first friend didn't seem to like her either.
Then came Halloween and he still didn't like Granger, with her believing she is smarter than everyone. Everytime he did better than her in class or knew something she didn't, she would nag him and try to imply he was cheating, somehow. Then after the troll incident suddenly, Weasley and Granger were adamant about how they were friends with Harry, despite Weasley not liking Granger originally and Harry avoiding her. He is sure that the two started spreading around the name of the 'Golden Trio' to try to bind them together.
After that, he repeatedly had heard the duo warning other students away from him. This caused Harry to become closer to Neville and his other dorm mates, in secret to try to get out from under Weasley and Granger's influence. The annoying duo would sometimes disappear for hours together and come back acting slightly different or trying to get Harry to do something, like investigate Nicolas Flamel and three headed dogs. He could only assume that they were making more plans about becoming closer to him.
Once he was aware of those two manipulating him, he began to wonder why they would be trying to be his friend.
Neville explained how magical families usually apparate or take the floo to get to the platform, so the Weasleys being on the muggle side of the platform and being so loud about muggles was incredibly suspicious and reeked of a set up. Dean and Seamus checked his booklist when they found out that he had grown up with muggles and it was clear he didn't know as much as he should even being muggle-raised. They noticed he was missing extra books that muggleborns are given to settle into the wizarding world better, such as: books that help with potion ingredient cutting techniques, laws relating to muggles and wixen, magical creatures, magical languages and politics, even information on tutors you can get during the summer was missing from his list.
Dean and Seamus were able to order the books and get the information from muggleborns from other houses, so Granger and Weasley wouldn't find out. The group suspected Harry had a mail redirection ward, as he had never received fanmail even while at the Dursleys' and he never got any letters other than from Hagrid, the Weasleys and his broom from Professor Mcgonnagal.
They noticed how Granger always tried to control what was able to Harry read, including checking out books from the library he needed to prevent him doing well in his assignments, and if she couldn't prevent him from researching for his classes then it was Weasley's turn to distract him from learning with chess or exploding snap. Granger was still snappy when other people did better than her in classes and sometimes referred to herself as "the brightest witch of their generation". Where she got that idea from, the group didn't know as even if they didn't do better than her, several Slytherins and Ravenclaws had consistently better grades than her. A few Hufflepuffs were close behind her in marks and would probably soon pass her, after all Hufflepuffs did value hard work and determination.
Neville and Parvarti Patil started to tutor Harry in pureblood traditions and politics. Parvati caught the group studying in an empty classroom and they filled her in on all they knew once she swore an oath to keep it all secret. Parvati knew about politics in other countries as well as Britain. She knew which things a wizard could do in another country but not in Britain, as the ministry banned so much, simply because they couldn't do it. She began teaching the whole group more types of magic, nothing that could get them arrested as they mostly discussed theory of dark and black magic.
Harry as Heir to the Potters should have been given some of this political education already and Augusta Longbottom was distraught to find out that he knew nothing of his family's legacy and sent along any books she thought he might need. Parvati's family sent books about grey/light magic as anything else would get the students into trouble; they were always neutral in the war and believed that there is no 'evil' magic, it's your intentions that matter.
They eventually decided that Harry would hold back his talent and they would study in secret, until they figured out the whole truth. Harry went along with Granger and Weasley's plans to go after the stone, though he didn't believe Snape had anything to do with it. The group was of the belief that should Snape have wanted the stone, it would have been gone before anyone could do anything.
They theorised that the least likely person, the one they wouldn't ever suspect normally, must be the one after the stone. So, they had two names, Madame Pomfrey or Professor Quirrell. Madame Pomfrey wouldn't be suspected as she was just the mediwitch, not a professor, so she wouldn't be considered in a plot for the stone. Professor Quirrell was just so pathetic and afraid of his own shadow that they figured no one would suspect their jumpy professor of being malicious, or smart enough to go after the stone. There was even a nickname that some older students used to bully the professor, "Squirrelly Quirrell". Harry was one who was sure it was Quirrell; he mentioned that the defence classes sometimes gave him a buzzing in his scar, which they laughed at and called him a dark magic detector.
At the end of the course when he met with Quirrell and found out that he had Voldemort on the back of his head, Harry considered the man's offer carefully. The stone for his parents back. He wasn't particularly bothered about getting his parents back, other than having a way out of the Dursleys' house. However, he didn't particularly want a dark lord after him, should he not give him the stone. Eventually the choice was taken out of his hands when Quirrell lunged at him and Harry somehow turned him to ash.
When he woke up in the infirmary, he felt slightly guilty about having killed Quirrell but mostly angry that Voldemort didn't give him time to decide. Then Dumbledore tried to convince Harry that 'Love' is his power against the dark lord. Harry was hard done not to laugh in his face, but acted natural, like a normal eleven year old kid would after having been through such an ordeal, but still showed an appropriate amount of awe for the headmaster.
He was suspicious of the headmaster after having left the stone in the castle, where anybody could have gotten it, particularly when he made the ominous warning about the third floor. The tasks seemed too easy to the group, like Dumbledore wanted someone to try to get to the stone. Harry also knew that Dumbledore held a lot of political power in their world, as Headmaster of Hogwarts, Supreme Mugwump of the International Confederation of Wizards, and Chief Warlock of the Wizengamot. No one would ever be able to go against him and win; he was just too influential after defeating Grindelwald. As far as Harry knew, everyone practically worshipped Dumbledore and thought he was always right. This made Harry's group of real friends very wary of him. Anyone seen as infallible was dangerous.
He was the leader of the Light in the war and was supposedly very close with the Weasley family and supported muggleborns so much that he got wizarding holidays banned so they celebrate Christian ones. They couldn't definitively say he was the one who directed Granger and Weasley this year in watching over Harry and controlling him, but they were all very careful to act a certain way in front of Dumbledore, just in case. They would need proof if they wanted anyone to believe them and they didn't have a way to tell just who is loyal to Dumbledore.
Flashback over
Dashing down to their abandoned classroom in the abandoned area of the dungeons, he was on watch to make sure he wasn't followed. The trio of Hermione, Ron and Ginny had been keeping a closer eye on Harry after Sirius died, constantly checking if he was okay and saying "It's okay to grieve, we're here for you' and then running off to tell Dumbledore anything he says. After Harry went off on Dumbledore for hiding things, he wasn't as trusted to be the good little Boy-Who-Lived that they wanted. For years, he had followed what they said and studied secretly, being tutored during summers when he could, letting those imbeciles believe he trusts them above anyone. He knows exactly how to regain their trust and what to say to get them to forget all about his little slip in blaming Dumbledore and not trusting him in everything he does for his "Greater Good". He's just waiting for the right time; he also needs to calm down before he kills them.
The group's classroom was the same abandoned classroom Parvarti had found them in, in first year. Only now it was far bigger, and more well hidden. Wizarding space was an intriguing concept to Harry and more than a little bit 'Doctor Who', so he immediately began learning all about it when Neville made an off-hand comment about people living in trunks.
Another interest of Harry's was blood magic. Blood is one of the most powerful ingredients to use in magic, and truly unique to your person. He thinks his mum used blood magic to save him, as it would be the only thing powerful enough to reflect a killing curse.
Runes are used for creating wizarding dimensions, but even that has its limitations due to many variants, such as: power of the wizard, what was used to carve or write the runes, what the runes were written on and the language of the runes. Runes are a very precise type of magic and magic is all about intent. A rune can be used for completely opposite things depending on the intent of the person drawing it. So, while choosing the right rune is important, you also have to keep your intent in mind.
Harry theorised, in second year, that if he drew the base for the wizarding space in parsel-runes with blood, he would be able to expand to a far greater size, whilst keeping it hidden from anyone who didn't have their blood written into the runes. Even if people added their blood to the runes after, they wouldn't have been in the original rune base, so they would gain access to a smaller space within, but separate to the group's dimension. Harry personally, would have to add people to the rune base as it requires a parseltongue spell that he created to test a person's true loyalty, if they were loyal to Harry or even merely against Dumbledore then they would be accepted. Only Harry had the ability to remove people from the dimension, though he was debating creating a rune sequence or spell to enable Neville to add or remove people.
As Harry activated the runes with a push of his magic into the detailed carvings in the wall next to the door, he watched the room expand into a castle in its own right within Hogwarts' walls. They created the separate dimension together: Harry, Neville, Parvati, Dean and Seamus.
Harry wanted a safe room to be undetected and warded, so he could create new spells and wards; practise banned magic and perform rituals in. Seamus wanted a room to duel in with increasingly difficult opponents. This caused Harry to create dummies which would be able to take on a person's looks, similar to polyjuice for an hour, as well as their duelling ability. All he had to do was add hair, blood or skin to the dummy console, a flat slab of quartz in a closet next to the dueling room, and the person would always be able to duel that specific person as long as they said the name of their desired opponent.
Dean knew they were going to need a library to hold all of their books, so he created that room, it could instantly be expanded should they need it. Neville wanted greenhouses and their own lake, so they set about creating their own home within Hogwarts. Harry created new wards, so that the sheer amount of magic in the small classroom that located their home was hidden, as well as a new secrecy spell.
Secrecy spells in general were severely flawed in his opinion. One spell makes it so you cannot speak a secret, but it can still be read from your mind. Another kills you should you share a secret, which is mighty suspicious, if you're trying to keep something hidden. Truth serum can get passed a lot of different truth spells depending on the dosage and potency. Harry's spell creates a subspace within your own mind to keep the secret. You cannot tell a secret that you can't remember and it cannot be read from your mind. His premise was simple: should actively be considering telling someone the secret, then the event enters the subspace, so you cannot tell someone. After a day, the event re-enters your main mind space and you remember. Should the event be in the subspace and someone 'in the know' speaks of it to you, the memory will re-enter your main mind again. In addition, Harry didn't want the spell to make you unable to talk to anyone about the secret, so he connected some spells in his spell-weaving to make you able to tell anyone who also knows the secret about it.
Once he had created the spell in English, he translated it to parseltongue as he does with most spells he creates. Parseltongue is well known to make spells stronger, and follow the caster's intentions more precisely as it is a magical language.
They named their home, "Erinyes Castle". Erinyes were deities of revenge, so the group thought it quite fitting. After all, this castle was to be used to plan against everyone controlling Harry.
The room opened into a large foyer, with a high ceiling and an arched doorway on the left, leading to a dark staircase downwards toward dungeons, a potions lab and a wine cellar. There was a large rounded staircase which Harry knew would lead to the entrance to the library, a training/ duelling room and a ritual room, where he created his spells and wards. To the right was a large glass doorway leading to the rest of the castle, including towers and a ballroom, which they rarely use, as well as sitting rooms and bedrooms. The whole foyer had dark wooden floors and smooth stone walls, with a glass chandelier hanging down from the ceiling, refracting light all around.
He knew he needed to release his anger, so he ran up to the duelling room and hissed, "Dumbledore" at the dummy, barely able to keep from slipping into parseltongue. As soon as the dummy had transformed into that old coot, he cast the first spell, wandlessly severing the old man's left hand. The dummy immediately began casting and moving around. The best part about duelling Dumbledore was that he gave Harry an actual challenge. All of the other dummies he tries, he defeats very easily, even when he ties one hand up or makes himself temporarily deaf. Dumbledore may be a manipulative, conniving old man, but he was undoubtedly powerful and an experienced duellist.
The duelling room contained a massive amount of weaponry, muggle guns, swords, knives, daggers, spears and even a crossbow. The weapons are mostly for the opponents however, as Harry made sure each of his friends had a blood-locked set of daggers and guns that they could summon from any distance.
Harry rarely shielded in duels, preferring to jump and twist to avoid getting hit. By now, Dumbledore is looking haggard and vicious with his hexes getting slightly darker than the initial set, when he realised that Harry is no easy opponent. The thought gives Harry an idea to give the dummies the memories of their past duels with the person they're duelling. As of now, they only duel as the person they're based off of would, but if they kept their memories of past duels, they may learn and provide more difficult duels. Harry is wary of adding anymore features to the dummies as they may actually become sentient if he puts too much "personality" or soul into them.
Swiftly, Harry removes the wand from the dummy's hand and watches as Dumbledore snatches up a gun. Spells are far easier to avoid than bullets. The speed of a spell cannot reach the speed of a bullet and it tests his reflexes even further. He dodges a bullet, barely grazing him before firing a few dark spells to slowly destroy his muscles and organs the more worked up he gets, now he just has to wait for Dumbledore to kill himself; that always cheers him up.
He's glad that Parvarti recommended dancing and gymnastic lessons to help each of them in combat. Originally, it was to help with etiquette lessons as Harry and the other boys dearly needed it. Neville was aware of how he was supposed to act, he just wasn't used to it and none of them were smooth or elegant enough for Parvarti. She hired instructors to teach them to dance and then gymnastics later when she realised the lessons were helping with their duelling. They each learnt to be graceful and deadly.
As the old man's dummy falters in it's movements, the gun clattering to the floor, Harry knew that the spell had reached his heart. With a swift Diffindo, he severed the man's head and the dummy reset as a blank again.
Sighing, Harry wandlessly cleaned himself and the room up until everything was back in place and he was presentable enough to go back to the dorms. Normally, he would stay in Erinyes Castle for dinner and then spend some time creating a spell but with how the youngest Weasleys and Granger are watching him lately, he knows he needs to go back.