In fanfiction, the possibilities are endless. It could be that they go on an adventure to a previously unknown magical land or face a powerful dark wizard who was thought to be defeated.
Well, it could go in many directions. They might travel to a previously unknown magical realm or encounter creatures that were only hinted at in the original series.
Well, if Harry Potter finds Excalibur, it could completely change the wizarding world. He might gain some new powers from the sword. Maybe he could use it to defeat Voldemort in a more epic way than with his own wand. It could also bring a new alliance between the wizarding world and some other magical beings who respect the power of Excalibur.
Another scenario could be that Ginny accepts but on the condition that they go on an adventure first. They could travel around the wizarding world, visiting different magical places they've only heard about, like the hidden valleys in Romania where dragons roam, before settling down to plan their future together.
Well, if Harry Potter was kidnapped by Loki, it could be a total chaos. Loki might use Harry's magic for his own devious plans. Maybe he wants to take over Hogwarts using Harry's knowledge of the school's secrets. Or he could be trying to trade Harry for something valuable in the wizarding world. Another possibility is that Harry would try to outwit Loki with his own brand of cleverness and magic, leading to a battle of wits between the two.
Snape could be very cold at first, but then his natural instinct as a healer (since he is quite good at potions which are often used for healing) might take over. He might give Harry a potion to ease the pain and start to patch him up. All the while, he would probably be scolding Harry for being so reckless and getting into a situation where he got injured.
One possibility is that Ginny would be overjoyed. She has loved Harry for a long time. She might immediately say yes and then they would start planning their future together. They could think about where to live, perhaps near the Burrow or at Hogwarts if they both end up teaching there. Their friends would be very excited too, and there would be a big celebration at the Burrow with lots of Weasleys and their friends like Hermione and Ron all gathering to congratulate them.
Well, he could encounter some dark artifacts that have a strange pull on him. Maybe he stumbles upon a cursed object that starts to influence his thoughts in a negative way. Since Knockturn Alley is full of dodgy characters, he might also be recognized by some Death Eaters in hiding, which would put him in great danger.
Well, if Harry Potter absorbs the Goblet of Fire in fanfiction, he might gain some extraordinary powers. Maybe he could control fire in a way that no one else can. He could use it to protect himself and his friends from the Dark Arts. It could also make him a target for more powerful dark wizards who want to use his new power for their own evil purposes.
Well, he could encounter all sorts of supernatural beings in Mystic Falls. Maybe he'll meet vampires and use his magic to either protect himself or try to understand them. Since he's used to dealing with magical creatures in his own world, he might approach the vampires with a mix of caution and curiosity.
Well, he might discover a whole new world of magic in that fanfiction. Maybe it contains spells that are not in the original books. He could get inspired to try out new things or it could even lead him to new adventures within the Hogwarts library, like finding a hidden section related to the ideas in the fanfiction.