One common theme is power dynamics. Since 'godlike sans' is, well, godlike, it often changes the power balance in the 'High School DxD' world. Another theme could be the clash of cultures, as 'sans' comes from a very different universe compared to the one in 'High School DxD'.
In these fanfictions, a frequent theme is the exploration of new abilities. As 'godlike sans' enters the 'High School DxD' world, his powers might combine or interact in unexpected ways with the existing abilities in that world. Another common theme is the protection of the world or a particular group. 'godlike sans' might take on the role of a protector in the 'High School DxD' universe, which is often full of threats and challenges.
Well, a lot of them deal with friendship and rivalry. The characters from both universes might become friends or rivals. Also, there's the theme of adaptation. 'godlike sans' has to adapt to the new rules and social structures in 'High School DxD'. And sometimes, there's a theme of redemption or self - discovery for the characters involved in the story.
Yes, there are some. You can start by looking on fanfiction platforms like Archive of Our Own. There are often various takes on crossovers like this, but the quality can vary. Some might focus more on the action elements from 'High School DxD' while incorporating the unique characteristics of 'godlike sans'. It's really a matter of personal taste when it comes to finding one you'll like.
One interesting plot could be Godlike Sans using his unique abilities to help the characters in High School DxD in battles. For example, his teleportation skills might give them an edge in combat against powerful foes.
He might fit in by becoming a teacher or some sort of mentor at the school. Since he has such great power, he could teach the students new ways of using their own powers or just general combat skills. In the process, he'd get involved in all the drama and power struggles within the school, adding a new dynamic to the story. He could also have his own goals and motives that are slowly revealed as the fanfiction progresses.
He might also interact with Rias. Rias is a powerful devil and a leader. Sans could approach her with his laid - back attitude. She might be initially suspicious of him but later come to respect his abilities. They could have some strategic discussions about dealing with common enemies in the High School DxD world. And Sans could probably crack some jokes that would either amuse or baffle Rias.
Transformation is also a popular theme. Given ACNologia's nature, fanfictions may involve him undergoing some sort of transformation, either physically or in his personality. This can be due to the influence of the High School DxD environment or his interactions with the characters. And this transformation can then drive the plot forward in interesting ways.
Friendship is also a big theme. Characters from both universes form new friendships and alliances. For example, Naruto's idea of comradeship might influence the characters in High School DxD and vice versa. They learn from each other's values and work together to face challenges, whether it's school - related in the High School DxD setting or something more global like in Naruto's world.
One common theme is the exploration of relationships. Given the nature of the original series, many fanfictions focus on the romantic or friendship relationships between Uri and other characters.
One common theme is power growth. Many fanfictions focus on the main character getting stronger in the High School DxD universe, whether it's through new powers or better control of existing ones.
One common theme is Asia's growth. Since she starts as a rather timid character in the original, fanfictions often focus on her becoming stronger. Another theme is her relationships, like her friendship with the main characters.
One common theme is power growth. In both Naruto and DxD, the characters are constantly striving to become stronger. Fanfictions often combine these two elements, showing how characters from one series adapt to the power - up systems of the other. For example, Naruto characters might learn about the Sacred Gears in DxD.