A plot could involve a time - travel scenario. Maybe Hermione discovers a spell that accidentally sends the four of them back in time to the founding days of Hogwarts. There, they have to deal with the original founders' rules and politics while also trying to find a way back to their own time. Blaise and Draco could be especially out of their element in this very different Hogwarts, and Harry and Hermione have to help them adjust.
One plot idea could be a story where Blaise and Draco have to team up with Harry and Hermione for a special magical tournament. They start off as reluctant allies but gradually learn to respect each other's skills. Another could be a mystery - something strange is happening at Hogwarts and the four of them must put aside their differences to solve it. For example, students are losing their magical abilities one by one, and they suspect a dark magic artifact hidden in the castle.
There could be a story where a powerful dark wizard threatens the wizarding world. The Ministry of Magic decides to form a special task force consisting of Blaise, Draco, Hermione, and Harry. At first, there is a lot of tension within the group due to their past rivalries. But as they face various challenges and dangerous spells cast by the dark wizard, they start to work together more effectively and even become friends.
A plot could be set post - Hogwarts. Draco and Blaise are trying to redeem their families' reputations in the wizarding world. Hermione, being the brilliant witch she is, is working on some important magical research. Their paths cross when a dark magic artifact resurfaces. Hermione believes it can be used for good if studied properly, while Draco and Blaise are worried it will fall into the wrong hands again. So they team up to protect it and study it.
One idea could be a story where they are all assigned to a special project at Hogwarts. Blaise, Draco, Hermione, and Theo have to put aside their differences and work together. Maybe it's a research project on a long - forgotten magic that could potentially be dangerous if misused. As they dig deeper, they start to understand each other better. Hermione's knowledge, combined with the Slytherins' cunning, makes for an interesting dynamic.
Another idea is that the OC is a Muggle - born with an amazing talent for potions. They end up in a class project with Harry, Draco, and Blaise. Their different approaches to the project (Harry's courage, Draco's ambition, Blaise's shrewdness) and the OC's out - of - the - box thinking create a really interesting dynamic as they compete and also learn from each other.
One plot idea could be that Draco and Blaise kidnap Hermione as part of a misguided attempt to gain some sort of leverage in the wizarding war. Maybe they think they can use her knowledge to find a way to end the conflict on their terms. Another could be that they believe she has a hidden power or secret that they want to uncover for their own gain. For example, they might think she has a connection to a powerful magical artifact that they are desperate to get their hands on.
One idea could be a story where Draco, Harry and Hermione are forced to work together on a special magical project for the Ministry. They start off hating each other but gradually come to respect one another's skills. Another plot could involve them getting trapped in an alternate magical dimension where they have to rely on each other to find their way back. Maybe Draco has some knowledge of the dark magic that created the dimension, Harry has his Gryffindor courage to lead them through dangerous areas, and Hermione uses her vast knowledge to figure out how to break the spell that trapped them.
Perhaps they were separated at birth due to some dark wizard's plot. As they grow up, they start to notice strange similarities in their magical abilities and instincts. When they find out they are triplets, they join forces to uncover the mystery behind their separation. They might face many obstacles, like opposition from their respective families who have different beliefs and values. Harry's Gryffindor - like courage, Draco's Slytherin cunning, and Blaise's own unique traits would all play a part in this adventure.
One idea could be that Hermione is turned into a vampire against her will and Blaise, who has been a vampire for a long time, takes it upon himself to teach her how to control her new powers. He could introduce her to the vampire society and they end up falling in love during the process.
A possible plot is a mystery - solving one. There's a strange magical occurrence in Hogwarts that is affecting both Gryffindors and Slytherins. Hermione starts investigating, and she enlists the help of Sirius (who could be a ghost or somehow back in a semi - corporeal form). Harry is naturally drawn to help Hermione, and Draco gets involved because it might affect his family's standing. As they dig deeper, they find out that it's an ancient curse set by a long - forgotten wizard, and they have to find a way to break it using their combined skills and knowledge.
One plot idea could be that the Marriage Law forces Hermione and Blaise together. At first, they are very reluctant and constantly bicker. But as they get to know each other's intelligence and hidden depths, they start to develop a grudging respect. Eventually, they find common ground in their love for knowledge and magic, and their relationship evolves into a real marriage.
One interesting plotline could be Draco and Blaise competing for Hermione's attention in a magical school setting. Maybe they start off as rivals but then realize they have more in common when it comes to their feelings for Hermione. Another could be a story where Hermione has to choose between them while they are all involved in a dangerous adventure against dark magic.