Issei is an obvious choice. Given his role as the main character in the series, he would likely be in the center of any story involving torture magic. Rias Gremory could also be involved as she often protects her comrades and would not stand by while they are subjected to torture magic. Akeno Himejima might be involved as well, especially if the torture magic has some connection to her powers or past.
Well, Xenovia could be a character involved. Her strong will and combat skills would make her a key figure in dealing with the threat of torture magic. Asia Argento might also be part of the story. Since she has healing powers, she could be crucial in helping those who have been affected by torture magic. And then there's Kiba Yuuto, who could use his swordsmanship to fight against those who use torture magic.
Akeno could also be a possibility. Her calm and sometimes mysterious nature might draw Kaido in. Their interactions could start with mutual respect due to their combat abilities and develop into something more romantic over time.
A half - devil, half - human hybrid who has been hidden away from both worlds. This character could have a struggle with their identity, not fully belonging to either the devil or human side. Their powers could be a combination of both, which would make them a very interesting addition. They might be discovered by the main characters and then have to figure out where they stand in the grand scheme of things.
A possible plot in High School DxD Torture Magic Fanfiction is that there is a magical artifact that is powered by torture magic. Different factions in the High School DxD world are vying for this artifact. The story could follow the main characters as they try to either obtain the artifact for good reasons or prevent it from falling into the wrong hands. Along the way, they face many challenges related to the torture magic associated with the artifact, like having to resist its corrupting influence.
Yes, one positive aspect could be the exploration of a character's strength. Through enduring torture, a character can show great resilience and determination, which can be inspiring.
Obviously, Aria herself is the main character. Her family members like her mother and father could be important characters, offering support or having different opinions. Her best friends would also be likely to be involved, providing emotional support or getting into some friendly arguments about how she should handle the pregnancy.
A futa version of Rias could be an interesting main character. She could have all of Rias's charm and leadership skills, but with the added element of her futa nature, which could lead to different power manifestations and relationship developments, especially with Issei.
Well, there could be her best friend who is always there for her during the pregnancy, giving her advice and emotional support. There might also be a mysterious figure, like an old wise woman who has knowledge about pregnancies in special circumstances that Tera Faya's case might be. And of course, there could be a rival of some sort, who might try to use her pregnancy against her in some way.
Igneel could also play a role. Since Igneel was Natsu's adoptive dragon father, he could appear in Natsu's mind during the transformation, guiding him and giving him advice on how to handle his new dragon powers. And there could be other dragons in the story as well. They might be either friendly or hostile towards Natsu depending on their nature.
There could also be new characters introduced. Maybe other magizoologists from different parts of the wizarding world. They could have different approaches and beliefs about magical creatures. Some might be rivals, trying to outdo Harry in the discovery and study of new species, while others could be mentors, guiding him in the complex world of magizoology.
Obviously Ranma herself. Her father Genma could also be a major character as he has to deal with his daughter's new permanent state. Akane could be there too, and their relationship would likely be very different. Instead of the typical boy - girl rivalry, it could turn into a more complex female - female dynamic.