Perhaps the story could focus on a hellhound and a human forming an unlikely friendship. They could face challenges together, like dealing with the social stigma in Helluva Boss's world of such an odd pairing. The human could introduce the hellhound to human concepts, and the hellhound could show the human the secrets of the hellish realm.
Some of the antagonists from Helluva Boss could also be important characters in the fanfiction. They could try to disrupt the relationship between the hellhound and the human. Maybe a powerful demon who doesn't like the idea of a hellhound getting involved with a human and tries to stop them, creating a lot of conflict and action in the story.
One idea could be exploring the backstories of the minor characters in more detail. For example, delving into Moxxie's childhood and how it shaped him into the imp he is today. Another could be a crossover with another similar animated series, like mixing the Helluva Boss universe with Hazbin Hotel and seeing how the characters interact. Maybe a fanfic could focus on Blitzo's relationship with his family and how it affects his work at I.M.P.
One interesting concept could be how a human character adapts to the chaotic and demonic world of Helluva Boss. Maybe they have to learn new rules, deal with different species, and face moral dilemmas that are unique to that setting.
One idea could be an OC who is a half - demon, half - angel trying to find their place in the Helluva Boss universe. They could have unique powers that come from both sides of their heritage and face discrimination from both demons and angels.
One idea could be a crossover with Hazbin Hotel. The characters from Helluva Boss could interact with those from Hazbin in the chaotic afterlife setting. For example, Blitzo could try to hire some of the Hazbin characters for a job at I.M.P. Another idea is a crossover with a more mainstream series like Adventure Time. Picture Moxxie and Millie exploring the Land of Ooo and having to deal with its wacky inhabitants while also trying to complete a hit. Or perhaps a crossover with My Little Pony. The contrast between the dark and raunchy world of Helluva Boss and the colorful, friendship - based world of My Little Pony could create some really interesting and comical scenarios.
One idea could be to have the characters from Helluva Boss somehow end up in the world of The Loud House. Maybe Blitzo and his crew are on a mission and accidentally cross dimensions. Another idea is a crossover where the Loud siblings get involved in the chaotic business of I.M.P. from Helluva Boss.
One plot idea could be Fizz and Ozzie facing a challenge in their relationship due to external pressures in the Helluva Boss world. Maybe there are other demons who don't approve of their relationship and try to break them apart.
Some of the more popular human characters could be those who form unexpected alliances with the main Helluva Boss characters. A human who teams up with Blitzo, for instance, and helps him with his assassination business in a way that no other demon could. This human might have a unique skill set or perspective that makes them stand out in the fanfiction community.
Well, perhaps in the fanfiction, the Hellhound King has a connection to an ancient prophecy. Percy is tasked with either killing it or taming it to fulfill the prophecy. As Percy delves deeper, he realizes that the Hellhound King has a complex personality and motives that are not just about destruction. It could also be that the Hellhound King has a hidden lair full of secrets and treasures that Percy needs to explore for some reason, like to find a weapon to defeat a new threat.
One idea could be the hellhound having a secret bond with Percy. Maybe it starts out as a dangerous encounter but as Percy tries to understand the hellhound's motives, they form an unexpected alliance. This could lead to them facing off against common enemies in the Percy Jackson universe.