A Spiderman and Highschool DxD fanfiction might involve Spiderman teaming up with Issei. Spiderman could teach Issei some new combat moves based on his acrobatic fighting style. And Issei could introduce Spiderman to the unique aspects of the Highschool DxD world, like the different factions and the power of Sacred Gears. They could go on adventures together, facing off against powerful foes that threaten both their worlds.
The Highschool DxD manga has indeed finished. It wrapped up after completing all the planned story arcs and providing a satisfying conclusion for the readers.
A 'Naruto Bijuu Highschool DxD' fanfiction might have some really cool crossovers. For example, the Bijuu could be seen as a new kind of power in the Highschool DxD universe. The students might be in awe or fear of Naruto and his connection to the powerful Bijuu. And Naruto, being the friendly guy he is, could try to use his powers for good in this new and different environment, like helping out in fights against the evil forces in the DxD world.
It would probably be really interesting. Naruto's skills and abilities as a 'god' would likely disrupt the normal flow of the Highschool DxD world. Maybe he'd use his ninja techniques in battles against the devils and angels in that universe.
Well, the Skyrim Dragonborn in a Highschool DxD fanfiction could be a really powerful and mysterious character. They might have their dragon - slaying skills and Thu'um at their disposal. Maybe they would be seen as an outcast at first because of their different abilities, but then prove themselves in battles against the devils or other threats in the DxD world.
If Spawn were to interact with the main characters, he would bring a whole new level of seriousness. He has a dark past and a lot of baggage. When it comes to Issei's goal of becoming a harem king, Spawn might find it absurd but also interesting in a way. He could offer his own perspective on power and how to use it responsibly, which would be a contrast to the more carefree attitude of some of the Highschool DxD characters. And with the other characters like Akeno and Koneko, he'd be sizing them up, trying to figure out if they're threats or allies.