Another theme is the mystery surrounding the Great Ones. Fanfictions often try to uncover more about their origins, their motives, and how they interact with the world of Bloodborne. This can involve delving into the lore of the game and expanding on it in creative ways.
Bloodborne's story is set in a gothic horror world full of beasts and dark secrets. You play as a hunter trying to uncover the mysteries and survive the nightmarish encounters.
Well, Gehrman, the first Hunter, would make an excellent main character in such a fanfiction. He has a deep connection to the secrets of Bloodborne. When an Old One crosses over, he would be one of the first to sense the change. His knowledge and skills could be put to the test as he tries to figure out what to do. Also, the Doll could play a significant role. She could be a mediator between the Hunter and the Old One, perhaps trying to understand the Old One's intentions and communicate them to the Hunter.
Well, a cool concept is the power dynamics. In fanfiction, the Old Ones are extremely powerful entities. So, in a crossover, they could disrupt the power balance in Bloodborne. They might introduce new forms of blood magic or madness that the Hunters have never seen before. Also, the cultural clash between the two universes can be fascinating. The Old One's way of existence might be completely different from what's known in Bloodborne, leading to all sorts of interesting plot developments.
The mystery. The world of Bloodborne is full of it, and 'Great One Hunter' fanfics often explore the unknown aspects. For example, the nature of the Great Ones themselves.
One popular 'Bloodborne Great One Hunter' fanfic is 'The Hunter's Ascent'. It delves deep into the psyche of the hunter as they face the terrors of the Great Ones. The author does an excellent job of describing the grotesque and otherworldly environments, making you feel like you're truly in the Bloodborne world.
A way to explore madness in the crossover is by having a character from the Bloodborne world try to use the knowledge or power of the Old Ones. Since the Old Ones are so far beyond human understanding, this attempt could backfire horribly. The character might start to lose their grip on their identity, their memories becoming muddled with the strange knowledge of the Old Ones. This transformation into madness could be a central part of the fanfic's plot, as the other characters then have to deal with this once - sane individual who has now become a threat due to their new - found madness.
One interesting plot idea could be a character from the Bloodborne world being transported to the realm of the Old Ones. They could struggle to adapt to the strange and eldritch environment while also trying to find a way back home. Maybe they discover secrets about the Old Ones that could change the very fabric of both worlds.