The characters from The Seven Deadly Sins could be brought into the Doom universe as allies or enemies of the Doom Slayer. For instance, Meliodas, with his great strength, could either team up with the Slayer to fight against the demons or be corrupted by the power of the Doom world and turn against him.
Perhaps the seven deadly sins are the root cause of the chaos in the Doom universe. The characters from The Seven Deadly Sins are summoned to the Doom world to atone for their own sins by helping to stop the demonic invasion. They each have to face their own 'sin - like' counterparts among the demons. For example, Escanor, who represents Pride in his own world, has to battle a demon that is the personification of excessive pride in the Doom universe. This would create an interesting dynamic between the two sets of characters and add a new layer of depth to the fanfiction.
In a fanfiction, the powers of The Seven Deadly Sins characters could be adapted to the Doom setting. For example, Ban's immortality could be a key factor in a battle against a particularly powerful Doom demon. He could keep getting back up and distracting the demon while the Doom Slayer figures out its weakness. Also, King's ability to control his sacred treasure could be used to help the Slayer navigate the dangerous landscapes of Doom.
She could be a foreigner who arrives in the Seven Deadly Sins' world with her unique ninja abilities. Her skills like shadow clones could be seen as strange and powerful in that world. Maybe she's on a quest to find a way back home and in the process, gets involved with the characters related to the Seven Deadly Sins.
One idea could be that the Doom Slayer has to face off against manifestations of the seven deadly sins in the hellish landscapes of Doom. For example, a demon representing Gluttony that constantly consumes everything in its path, and the Doom Slayer has to find a way to stop it from devouring all the resources he needs to survive.
In fanfiction, Hinata could represent Temperance in the Seven Deadly Sins world. She is calm and in control of her emotions, which is in contrast to the extreme emotions often associated with the sins. In the world of the Seven Deadly Sins, she could be a guiding figure, teaching others how to manage their emotions better. Rock Lee could be associated with Envy in an interesting way. He is always envious of those with more natural talent, but he uses this envy to fuel his own hard work and improvement.
In Percy Jackson fanfiction, the seven deadly sins can be incorporated as powerful forces or entities. For example, they could be ancient evils that the demigods have to combat. This adds a new layer of danger and conflict to the already complex world of Percy Jackson.
Ichigo could interact with Meliodas, the captain of the Seven Deadly Sins. Since Meliodas is very powerful, Ichigo might initially see him as a threat. But they could end up teaming up when a greater evil emerges. For example, a powerful demon that threatens both their worlds. They could learn from each other's fighting styles. Ichigo's fast - paced swordsmanship could be compared to Meliodas' own combat skills.
Naruto would likely be very friendly and curious about the characters from 'The Seven Deadly Sins'. He might try to befriend them quickly. For example, he would be excited to learn about Meliodas' powers and would probably challenge him to a friendly spar. The characters from 'The Seven Deadly Sins' would be a bit more guarded at first. But they would soon warm up to Naruto's positive energy. Ban might be interested in Naruto's ability to keep coming back in fights, much like his own immortality.
The RWBY characters would likely be initially cautious when interacting with those from Seven Deadly Sins. Ruby, with her innocent and curious nature, might be the first to approach and try to make friends. She would be fascinated by the different powers and cultures. Weiss, on the other hand, might be more standoffish due to her pride. She could see the Seven Deadly Sins characters as uncivilized at first. Blake might be more empathetic, especially if she encounters characters dealing with inner turmoil like the sins represent. Yang would probably be ready for a fight or a friendly sparring session right away.
Some characters might resist the influence through their strong willpower. Naruto, for example, with his determination to protect his friends and the village, could fight against the sin of pride. He would constantly remind himself of his roots and the importance of teamwork. Others may struggle at first but then find support from their comrades. Sakura could initially be affected by envy, seeing other female characters' abilities, but with the help of Ino and her other friends, she could overcome it.
Some characters could be directly linked. For example, a power - hungry character might represent greed. They constantly seek more magic power or rare items.
Naruto would probably be very curious about them. He'd start by asking a lot of questions. He might befriend some of them quickly, like he did with many characters in his own world. For example, he could bond with Diane because of her kind heart, despite her being a giant.