Well, if the fanfic has a strong protagonist from either universe who is very capable. For instance, if Hermione from Harry Potter teams up with the Cullens in Twilight. Hermione's intelligence and magical skills, combined with the Cullens' vampire abilities, would make for a powerful force against any danger. Just the idea of such a team would make you feel safe.
A fanfic that focuses on the friendship between a Hogwarts student and a Twilight vampire could be very comforting. Imagine a story where the vampire, with all their knowledge of the supernatural world, helps the student through a difficult time at Hogwarts. They could offer advice on how to deal with dark magic threats, and their presence would make the student (and the reader) feel safe.
One possibility is that the fanfic changes Snape's backstory to make him more sympathetic. Harry, being empathetic, then feels safe around him. For instance, if Snape's past is shown to be full of hardships that made him act the way he did, Harry might understand and feel safer in his presence.
In some fanfictions, it could be that the author has rewritten Snape's character in a more approachable way. Maybe Snape shows a side of himself that is protective towards Harry, like secretly guiding him in his magic studies without the usual harshness, which makes Harry feel safe.
One common scenario is when they are in a dangerous situation together, like facing a powerful dark wizard. Draco steps up and uses his skills and knowledge to keep Harry safe. For instance, in a fanfic where they are trapped in a haunted castle, Draco uses his Slytherin cunning to find an escape route for both of them, which makes Harry feel protected.
Comic books give a sense of security as they allow people to immerse themselves in a world where justice is served and good triumphs over evil. It's a comforting thought and can make one feel protected, even if just for a while.
No, Twilight was not a fanfic of Harry Potter. They are two completely separate and distinct literary works with their own unique storylines and characters.
The crossover is conceptualized by taking the core elements of both universes. Harry Potter's immortality could be a result of some dark magic he dabbled in, like the Horcruxes but with a different twist. In the Twilight world, the vampires are immortal in their own way. So, the fanfiction might explore how Harry's immortality, which is magical in nature, compares to that of the vampires. It could also look at how he might adapt to the new social structures in the Twilight world, like the vampire covens and the werewolf packs.
A more complex idea would be a plot where Voldemort somehow discovers the immortality of the vampires in the Twilight world. He tries to make an alliance with them to gain more power, but the vampires are hesitant as they don't want to get involved in the wizarding war. This would create a lot of political intrigue and power struggles.
Hermione Granger and Bella Swan could also be main characters. Hermione could bring her intelligence and knowledge of magic, while Bella could provide insights into the Twilight world. They might start off as rivals, with Hermione thinking Bella is too naive and Bella finding Hermione too bossy, but then they grow to respect each other and work together.
One idea could be a wizard from the Harry Potter world accidentally traveling to Forks. Maybe they mistake the vampires in Twilight for some kind of dark magic creatures. They could then try to use their magic to either fight or understand them.