In such fanfiction, usually the character uses a time - turning device or some magical spell. They then travel back with the intention of revenge. For example, if it's Harry, he might go back to when Voldemort was still a student at Hogwarts to stop him before he becomes a dark wizard. He could use his knowledge of the future, like knowing about the Horcruxes, to defeat Voldemort early and get revenge for all the lives lost in the original timeline.
One common theme is power dynamics. When Harry travels back in time to take revenge, he often has to deal with the power structures in the wizarding world that were against him before. For example, he might have to outwit the Death Eaters or the Ministry of Magic who were once obstacles.
One popular 'Harry Potter time travel revenge fanfiction' is 'Back in Time: A Potter's Revenge'. In this fic, Harry travels back and uses his knowledge to get revenge on those who wronged him. It has some really interesting plot twists.
There could be a fanfiction where Hermione time - travels to change the past regarding the treatment of house - elves. In a sense of revenge for their mistreatment, she uses her intelligence and knowledge of the future to start a revolution in the wizarding world for their rights much sooner. This would also have a significant impact on the overall story as the elves play important but often overlooked roles. It could lead to different alliances and power dynamics within Hogwarts and the wizarding community at large.
I'm not entirely sure. Fanfiction can cover a huge range of ideas, and while time travel in Harry Potter is a common theme, and Orochimaru is a well - known character from Naruto. The combination seems a bit out there. But, if you search on some major fanfiction platforms like Archive of Our Own or FanFiction.net, you might be able to find out for sure if such a fanfiction exists.
A great fanfiction idea could be that James Potter time - travels during a crucial battle in the wizarding world. He travels back to a time when the dark forces were just starting to rise. With his future knowledge, he could start preparing the wizarding community earlier. He could train young wizards and witches in advanced defensive magic, and try to change the course of history so that the big battle he left behind would have a different, more positive outcome.
Another possible antagonist could be some of the Hogwarts faculty who were either secretly supporting Voldemort or were too cowardly to oppose him. In a time - travel revenge fanfic, Harry might uncover their true natures and take revenge on them for not doing more to protect the students and the wizarding world from Voldemort's rise.
One great older Harry Potter time travel fanfiction is 'The Time - Turner Conundrum'. In this story, Harry accidentally travels back in time much further than he intended. It's full of interesting twists as he has to deal with a Hogwarts that's very different from what he knows, and he has to figure out how to get back to his own time without changing history too much.
Another interesting fanfiction plot could be about a descendant of Salazar Slytherin who time - travels. They go back to the time of the Basilisk with the intention of taming it. They believe that the Basilisk was misused in the past and that they can change its fate. They might have to face many challenges, like the opposition from other wizards at that time who fear the Basilisk's power.
One possible fanfiction idea could be that a character discovers a time - traveling device while exploring the Chamber of Secrets where the Basilisk once lurked. They accidentally travel back in time to the era when the Basilisk was first created or when Salazar Slytherin was alive. This could lead to all sorts of adventures, like trying to prevent the Basilisk from being created or changing the course of Hogwarts' history regarding the Chamber.