One possible plotline could be that Bellatrix, in a moment of unexpected self - reflection, decides to save Hermione from a dangerous dark magic experiment that the other Death Eaters are planning. Maybe she has a change of heart because she sees a bit of herself in Hermione's intelligence and determination.
Another plot could involve Bellatrix saving Hermione from a rival dark wizard. Bellatrix might want to keep Hermione alive to use her knowledge of magic for her own purposes later. She could then start to form an odd sort of alliance with Hermione, which would be full of tension and distrust at first but gradually develop into something more complex.
One possible plotline could be that Hermione discovers a dangerous curse about to befall Fred during a battle and uses her quick thinking and vast magical knowledge to counter it. For example, she might create a complex protective charm just in time. Another could be that Fred is trapped in a magical maze or trap, and Hermione uses her logic and spell - casting skills to break him free. Maybe she has to solve a series of riddles to get to him first.
One possible plotline could be that Harry uses a powerful spell he's been secretly practicing to stun Bellatrix just in time as she's about to harm Hermione. For example, he might use a modified version of the Stupefy spell that's more powerful. Another could be that Harry manages to create a diversion, like summoning a horde of magical creatures, which distracts Bellatrix long enough for him to rescue Hermione.
A great plotline is the redemption arc. Bellatrix, known for her extreme cruelty, could be influenced by Dark Hermione. Hermione might be on a path to use dark magic for what she believes is a greater good, and Bellatrix could see this as a way to redeem herself. This could lead to a lot of internal conflict for Bellatrix as she struggles with her past actions and tries to follow Hermione's lead. There could also be a plotline where they explore the limits of dark magic together. They experiment with spells and incantations that no one has dared to try before, and this exploration could either lead them to great power or their downfall.
One common plotline is Hermione being captured by Bellatrix and forced into a situation where she has to act like a pet. For instance, Bellatrix might use a spell to make Hermione obey her every command.
One possible plotline could be that Bellatrix, under some strange circumstances, is forced to teach Hermione magic in a very unorthodox way. Since Bellatrix is a Death Eater, she might initially try to corrupt Hermione with dark magic, but Hermione's strong will resists. Another could be that Bellatrix has some unique knowledge of an ancient magic that Hermione needs to learn for a greater good, like saving Hogwarts. They would have a very tense relationship filled with power struggles as Hermione tries to gain knowledge while Bellatrix tries to assert her dominance.
One possible plotline could be that Neji is severely injured during a battle against a powerful enemy. Naruto arrives just in time, using his newfound Sage Mode powers to fend off the foe. He then uses his medical ninjutsu skills, which he has been secretly training, to heal Neji's life - threatening wounds. Another plotline might involve Neji being trapped in a genjutsu created by a rogue ninja. Naruto, with his strong will and ability to break genjutsu easily, dives into Neji's mind to free him from the illusion.
One possible plotline could be that Kakashi arrives just in time to save Naruto from a powerful enemy's ambush. He uses his Sharingan to predict the enemy's moves and counter them effectively, allowing Naruto to escape unharmed.
One possible plotline could be that Naruto has to go through a series of dangerous trials in the enemy's territory to reach Sasuke. He might face powerful foes and have to use new jutsu he's developed. Another plotline could be that Sasuke is in a coma, and Naruto uses his chakra to somehow enter Sasuke's mind and fight off the inner demons that are keeping Sasuke trapped. Maybe Naruto also has to convince Sasuke's friends from his time away to help him in this rescue mission.
Well, in some fanfictions, Snape might be trapped in a magical trap set by Death Eaters who are still loyal to Voldemort's ideals. Harry, with his natural sense of justice and his loyalty to Hogwarts (where Snape also has a complex connection), figures out the trap's mechanism and manages to free Snape. Or perhaps Snape is on the verge of being attacked by a magical creature, and Harry, using his experience with magical creatures from Hagrid's teachings, scares the creature away and saves Snape.
Another plotline might involve Harry adapting to Bellatrix's rather extreme and unorthodox parenting style. He could be learning dark magic in a way that still aligns with his own sense of good, which would create a lot of internal conflict for him. Bellatrix, on the other hand, might start to have a change of heart as she sees Harry's positive influence on her in some aspects.