Hermione would probably try to understand Shendu from a logical and magical perspective. She could attempt to communicate with him to find out more about his powers and his weaknesses. Ron, on the other hand, would be more likely to jump into action if he saw Shendu as a threat. He might not be as diplomatic as Hermione and could end up getting into a scuffle with Shendu's minions. The three of them together would have to figure out how to deal with Shendu's different approach to magic compared to what they're used to in the wizarding world.
Well, perhaps Harry Potter could use his magic against Shendu's dark powers. For example, he might try to counter Shendu's spells with his own powerful incantations like Expelliarmus. It would be an epic battle of magic from two different fictional universes.
In a 'Harry Potter meets Apollo' fanfiction, their interaction would be quite complex. For starters, Dumbledore would surely approach Apollo with great respect, being aware of the power and significance of a god. Apollo might be interested in Dumbledore's wisdom and magic. The students, like Neville, could look up to Apollo as a new source of strength. Meanwhile, Apollo might see the potential in these young wizards and witches and decide to mentor them in some ways, sharing his knowledge of combat and strategy from his long existence in Greek mythology.
Harry would probably be a bit shy at first when meeting the Avengers. But he would soon start sharing his knowledge of magic. The Avengers might be curious and ask a lot of questions. For instance, Tony Stark would be eager to understand the principles behind magic.
Sometimes, other characters from the Harry Potter series might also be involved. For instance, Hermione could be part of the story. She might be intrigued by the encounter between Harry and Rowena and try to research more about Rowena's time. Her thirst for knowledge could lead to some interesting exchanges with Rowena. Another character could be Dumbledore, who might have some prior knowledge or connection to Rowena's magic that he shares with Harry during the course of the fanfiction.
Definitely Harry Potter and Finn Hudson. Harry is the hero in the wizarding world, and Finn is a key figure in the Glee club. They could bond over their leadership roles. Harry could teach Finn some magic tricks, and Finn could show Harry how to be more confident while performing in front of a large audience.
Probably Harry Potter and Edward Cullen. Since Edward is sort of the main character among the Cullens in a way, and Harry is the central figure in his world. They both have unique abilities and a sense of responsibility, so it makes sense for them to be the first to cross paths and start interacting.
Harry would likely be both curious and cautious when interacting with Death. He might ask Death many questions about the meaning of life and death in the wizarding world. Other characters like Hermione and Ron, if they are involved, would probably be very worried about Harry's interaction with Death and try to protect him or convince him to stay away.
At first, Severus would probably be very suspicious of Harry. After all, Harry is an unknown figure suddenly appearing. But Harry, being the friendly person he is, would try to break the ice. He might start by complimenting Severus on his potion - making skills, which Severus is already quite good at even as a young boy. Their interaction would be a bit tense initially, but as they start to understand each other more, they could become friends or at least allies.
The most interesting aspect is the clash of two very different mythologies. Harry Potter comes from a world of wands and spells, while Shendu is from a world of ancient Chinese magic and demons. When combined in fanfiction, it creates a unique blend of cultures and powers.
Hermione Granger is a very common character. Since she is Harry's best friend, she would likely be there to help him understand and control his new superpowers. She might research in the library to find out how these powers came about and how to use them effectively. Ron Weasley is also common. He would probably be both in awe and a bit jealous of Harry's new powers at first but would still support him in the end.