Another fanfic idea might be to create a prequel story. Show how the 'blood for blood' concept originated in the Bloodborne universe. It could involve the early experiments with blood, the first encounters with the otherworldly forces that led to the creation of this extreme ideology. The story could detail the fall of a civilization or a group of people as they delved deeper into the 'blood for blood' idea, leading up to the state of the world as we see it in the game.
One way is to base it on the existing blood - related mechanics in the game. Maybe a character discovers a new form of blood transfusion that has the power of 'Blood for Blood'. They could use it to either heal themselves by taking the blood of their enemies or gain new abilities. This would add an interesting twist to the fanfic and stay true to the game's themes.
The phrase 'Blood for Blood' in a Bloodborne fanfic could also symbolize a pact or an oath. Characters might swear 'Blood for Blood' to show their loyalty to a cause or to each other. Since Bloodborne has a lot of dark and mysterious factions, this could be a way for members to show their commitment, using blood as a binding force.
First, the atmosphere. You need to capture the dark, gothic feel of Bloodborne. Describe the decrepit buildings, the fog - filled streets, and the sense of dread. Second, the characters. Create hunters or other inhabitants with their own motives and backstories related to 'blood for blood'. Third, the action. There should be intense battles against the terrifying beasts, with lots of blood and gore, in line with the 'blood for blood' theme.
Clive Barker was inspired by his love for horror and the macabre. He took elements from classic horror stories and added his own unique twists. Also, his creativity in imagining new and terrifying creatures and situations contributed to the 'Books of Blood'.
Another interesting angle is a fanfic that focuses on a love story within the Blood of Eden ranks. Maybe a relationship that has to be kept secret due to the strict military - like structure of the group. This could bring in elements of drama and romance.
One idea could be a story where a group of adventurers has to complete a quest during the blood moon. They face strange and powerful creatures that only emerge during this time. The blood moon's red glow could have some sort of magical effect on their abilities, either enhancing or hindering them.
A 'blood and vengeance fanfic' could also be about a wrongfully accused character who has to fight for their life and clear their name while seeking revenge on those who set them up. They might form an unlikely alliance with other outcasts in the process.
Well, you could write a fanfic that focuses on the backstories of the characters in 'Blood of Olympus'. Maybe explore how Percy Jackson became the hero he is from a different perspective. Or create a plot where the gods interfere more directly in the demigods' quests in the fanfic. This could add more drama and tension as the demigods have to deal with the gods' complex personalities and motives on top of their existing challenges.
Perhaps a fanfic where Naruto's blood has some special connection to an ancient and powerful demon. The demon is slowly being awakened due to some dark magic related to Naruto's blood. Naruto has to face not only the threat of the demon but also the distrust from some in the village who think his blood is a danger. He must prove that he can control this situation and keep the village safe.
A good concept for a Blood x Alice fanfic might be a mystery - solving plot. Suppose there are strange disappearances in their world, and Blood and Alice team up to find out what's going on. Along the way, they discover secrets about their own pasts and the true nature of their world. Or, you could write a fanfic where they go on a journey to find a magical object that has the power to change the fate of their world. This would involve a lot of adventure, with them facing different obstacles and enemies.