Thanos would be a major character too. His quest for the Infinity Stones and his power - hungry nature would be a great contrast to the values of the wizarding world. His presence would force the wizards and witches to step up and defend their world. And if Voldemort teams up with him, he would be a double threat that the heroes have to face.
Hermione Granger would also be a crucial character. Her intelligence and vast knowledge of magic could be key in understanding the powers of the Infinity Stones and coming up with strategies to deal with them. She could also be the one to communicate with the Avengers if they come to Hogwarts, as she is good at dealing with new and complex situations.
In this type of fanfic, the Infinity Stones could have a very different effect in the Harry Potter universe. For example, the Time Stone could be used to reverse dark spells or resurrect fallen wizards. However, the Stones' power might also be limited by the magic rules of the wizarding world. The fanfic could delve into how the characters from both universes adapt to the presence of the Stones and how they use or misuse their power.
Well, it could be that Voldemort teams up with Thanos somehow. Maybe Voldemort is attracted by the power of the Infinity Stones. He could use the Time Stone to go back and change some key events in the wizarding world to his advantage, like preventing Harry's parents from being protected by the Fidelius Charm.
Well, Harry Potter could use his magic skills. For example, he could use the Patronus charm to fend off some of the alien creatures in Infinity War. His knowledge of spells like Expelliarmus could also be used to disarm the villains' weapons.
Well, George Weasley could be a main character. After losing Fred, he could be trying to keep the joke shop going while also dealing with his grief in a post - war world. Cho Chang might be another main character. She could be working with international wizards to strengthen relations between different wizarding communities after the war. And Seamus Finnigan could be part of the group. He could be involved in some magical research related to how to prevent future dark wizards from rising, using his experiences from fighting in the war.
The main characters could include some of the new generation as well. For example, Albus Potter or Scorpius Malfoy. They could be at the center of this 'war' in the fanfic, perhaps dealing with the consequences of their parents' actions. Ginny Weasley could also be a main character, as she's a strong witch in her own right. And then there are the Hogwarts professors. Professor McGonagall could be leading the defense of Hogwarts in this war - like situation, and Professor Flitwick could be using his magical expertise to help the side he's on.
It could be about the Mad Titan Thanos in his early days, before his full - blown obsession with the Infinity Stones. We might see how he first learned about the Stones and what led him on the path to collecting them all. Another possibility is that it could feature the Asgardians, as they had knowledge of at least some of the Stones. We could see Odin's early encounters with the Stones and how he dealt with the power they held.
Well, it could still be Thanos. His goal of collecting the Infinity Stones would be a great threat to Superman's world as well. Superman would have to figure out how to stop Thanos from using the stones' power on a galactic scale.
Harry Potter is surely one of the main characters. He is the central figure in the fight against Voldemort during the second war.
Harry could use the Mind Stone to read the thoughts of his enemies, like Voldemort. This would give him an edge in the fight against the Dark Lord. Hermione might use the Time Stone to gain more time to study and find solutions to difficult problems, like how to defeat a powerful dark magic spell.
Captain America could be the main character. He's always been a leader, and in the aftermath, he could be the one trying to hold the remaining Avengers together. He would be dealing with his own sense of loss and responsibility. He might also be trying to figure out how to prevent future disasters like Infinity War.