"To keep Connor safe. To always protect him. To insure that he lives as untroubled a life as he can, until he has to face Lord Voldemort again. To be his brother and his friend and his guardian. To love him. To never compete with him, never show him up, and never let anyone else know that I'm so close to him. To be ordinary, so that he can be extraordinary."
—Harry Potter's vows in regards to his brother, Connor Potter
Arc of Sacrifices, also known as Sacrifices Arc, is a Harry PotterAlternate Universe in which Harry's not only a Slytherin, but also a twin. That brother, Connor, wears the mantle of the Boy Who Lives, while Harry acts as his protector and guardian. The series is complete, featuring seven parts, each roughly paralleling the canon. It's notable for its story, a series twists and turns, and Alternate Character Interpretation. The author's page can be found here.The parts are, in order:
Altum Videtur - the Apollonis family teaches their children to speak Latin from an early age. Additionally, at Connor's gravesite, Harry says "Atque in perpetuum, frater, ave atque vale," which translates to "And now forever, brother, hail and farewell."
Ascended Extra - a couple of notable examples are Evan Rosier and Regulus Black, who aren't even alive during canon but both play important roles. Others include Millicent Bulstrode, Pansy Parkinson, and their families.
Beta Couple: Many. The most important is Connor/Parvati, but others include Hermione/Zacharias Smith, Millicent Bulstrode/Pierre Delacour, Honoria Pemberley/Ignifer Apollonis, as well as many of the married couples.
Played with in regards to Snape/Regulus, who never actually get together due to the latter's death. However, it's implied that they would have, and they're used as an interesting parallel to Draco and Harry nonetheless.
One of the defining traits of the Puellaris witches, who's greatest goal in life is to keep their husband and children safe. They are trained to be quiet, and submissive- in public. Threaten her children, and she literally becomes a lioness and bites off your head.
Brilliant but Lazy: Sort of, with the Weasley twins. For example, at one point the do something to Snape's wand that makes it so that every time he casts a spell, something cute happens, like a pixie, or a pink snake with little hearts on it, or kittens, etc. They accomplish this by making it so that Snape's wand core switches out of his wand every time he casts a spell, replacing it with a different core that casts the cute spell, all without harming his wand.
Definitely for Draco, who is really very smart, just rather lazy. It is later revealed that his laziness is his greatest flaw.
Children Are Innocent - played with. Lily doesn't exactly believe Harry himself is evil, just his magic which comes from Voldemort. Still, she never gave her son the choice to be good or evil.
Cloudcuckoolander: Thomas Rhangara, one of Harry's allies and a philospoher who declared Dark because he thought it made more sense than Light magic, and Honoria Pemberly, another of Harry's allies.
Crazy Jealous Guy: Draco, for Harry. He gets better at managing the possessiveness, later. Also, Michael Rosier-Henlin for Draco.
Creepy Twins - Sylvan and Oaken Yaxley, to the point where only one of them can exist at a time; the other one stays in an alternate dimension. They can swap in and out of reality. They manage this by taking the blood of unwilling sacrifices.
Dark Is Not Evil - Dark Magic is magic which subverts someone's free will, but doesn't have to be evil. In fact, many of the good guys are Dark wizards who aren't psychopathic killers and thus don't want to follow Voldemort.
Disproportionate Retribution: Inverted: Harry has suffered extreme mental and physical abuse, most of which carried itself into his psyche years after he finally broke the web that had held his magic and free will hostage for the better part of his childhood, thus causing him to never lead the normal life that Connor did despite the fact that Connor wasn't even the one who was supposed to save the world, all in the name of the Greater Good. Despite the fact that lesser instances of child abuse warrant the death penalty, Harry pleads with anyone who'll listen that what Lily, James, and Dumbledore did wasn't that bad. He even succeeds in convincing the Wizangamot to only put his parents into Tullianum for life. Indigena Yaxley fixes that soon enough.
Doorstopper - All of the books after the third are long, with Wind That Shakes the Sea and Stars having over 750,000 words, according to Fanfiction.net's word counter. The combined length of this entire series is about three times the length of the Harry Potter books.
Eye Scream - Harry to the Dark Lady Monika after he defeats Voldemort and absorbs his power; he laughs and one of her eyes bursts.
The Many snakes are a very poisonous breed of snake whose venom can kill a man in seconds. It can also cause someone to become irreparably blinded if it's spat in the eyes, as Harry effectively demonstrated with Voldemort.
Face-Heel Turn - Michael Rosier-Henlin. Supposedly Snape; it turns out that Voldemort was possessing him and made him do so.
At the end of A Song In Time Of Revolution, Adalrico, Hawthorn, and Lucius have been forcibly turned to Voldemort's side by way of their Dark Marks.
False Friend - Evan Rosier (although he didn't know it was him), and Michael Rosier-Henlin to Connor.
Family Honor - Eventually the reason Owen has to kill Michael.
Fantastic Racism - Werewolves face some pretty heavy prejudice for their curse, and as the books progress, laws begin to come into effect that stop werewolves from having paying jobs and custody of children.
Flat "What." - there are quite a number of them scattered throughout the stories, mostly in response to something Harry says or reveals.
Harry (pointing to a potion he's brewing): That's the first stage of a cure for lycanthropy, I think.
Killed Off for Real - anyone who dies won't come back. The only time this isn't played straight is with the can on example of Regulus Black, who apparently didn't die in the first place.
Lawful Stupid - Averted in-universe with Scrimgeour: while he despises Dark magic and "Lords mucking around in his ministry," it's acknowledged by Harry around the second time he shows up that he is by no means an idiot. Which makes Juniper's reign even more painful to witness in contrast.
Light is Good - The Light families in general. Arguably Harry himself whose ideals are closer to Light than Dark. The Light itself is much more decent and understandable than the wild Dark. "The Dark does not care what its Lords do in its name. I [...] do."
Lotus-Eater Machine: At one point Harry takes a Dark curse featuring this. Unlike some other incarnations of the trope, the perfect world in the curse doesn't turn into a nightmare, but it also takes an outside influence with knowledge of the Dark Arts (in this case, Lucius Malfoy) to convince him to break the dream world.
Magic Music - siren song comes loaded with compulsion, which Voldemort uses to his advantage near the end of the fifth book.
There's also Arabella Zabini, a Songstress who possesses the ability to create and dispel illusions and compulsions with her voice. She is even able to counteract the siren's song at one point to keep anybody from drowning themselves.
Mama Bear - Puellaris witches will turn into lionesses to defend their children.
Meaningful Name - Henrietta Bulstrode teaches Transfiguration under the name "Professor Belluspersona"; Belluspersona means "beautiful disguise".
Mood Whiplash - Chapter 66 of book 7 begins with Regulus's funeral, goes through some dramatic moments, and ends with a passionate interlude between Harry and Draco. True, it doesn't go from tragedy to comedy, but the latter half of the chapter lacks the gravitas of the first half.
My Master, Right or Wrong - Indigena Yaxley to Lord Voldemort; she follows him out of honour but hates the fact that she has to kill people that she respects.
Noodle Incident: Rufus Scrimgeour had one that involved involved a powerful illusionist, two cats, and green goo which is now the reason why the healers at St. Mungo's will only treat him for purely physical wounds.
Polar Opposite Twins - Harry and Connor, in the early books: Connor is 'innocent,' spoiled, Light, and Gryffindor, while Harry is 'tainted' at least to Lily and Dumbledore, suicidally selfless, Dark again, to Lily and Dumbledore, though he also appears as such to most Light families - he's really a mix of the two, and Slytherin. But really, that just touches the tip of the iceberg, and they become more sympathetic to each other as they get older.
Pretentious Latin Motto - a number of pureblood families have Latin mottos. These include the Bulstrodes (Duramus - we endure), and the Yaxleys (Vita desinit, decus permanit - life is fleeting, glory remains).
Pyrrhic Victory - although Harry survives, many people he loves, such as Regulus, Narcissa and Connor, do not make it.
Relationship Reveal - pulled in-universe, when Harry reveals to a crowd of people that he and Draco are going through a joining ritual. (Of course, the reader and Harry's allies already know this.)
Sacrificial Lion - Sylarana, at the end of the second book, which is the first truly important death.
Self-Immolation - How Charles Rosier-Henlin kills the Death Eaters threatening his family.
Self-Sacrifice Scheme - Subverted, both times. Peter planned to die for the Horcrux wand, but Regulus beats him to the punch. Later, Harry planned to die for the final Horcrux, but Connor kills himself before he gets the chance.
Shipper on Deck - quite a few characters ship Draco/Harry before anything actually happens between them.
Triang Relations - Harry, Draco and Michael Rosier-Henlin have Type 4, with Draco and Harry as B and C respectively. Draco is aware of Michael's interest in him, and often intentionally leads him on. Of course, Harry is not pleased when he finds out.
Voluntary Shapeshifting - multiple Animagi. As well as the ones mentioned in canon, Harry can turn into a lynx, Draco can turn into a white fox, and Connor can turn into a boar.