I'm not entirely sure specifically what that fanfiction is about. It could potentially be about Bill Cipher achieving or obtaining Will Cipher in some way, perhaps in a strange or otherworldly scenario within the context of the Gravity Falls universe. It might involve some sort of power play or a very unique plot device that only fans who have read it would know for sure.
Well, in some fanfictions, Bill might kidnap Will to gain more power. Maybe Will has some special ability or knowledge that Bill wants to use for his own evil plans.
Will might find a way to escape on his own. Since he is also a Cipher, he could have some hidden powers or tricks up his sleeve. Maybe he manages to outwit Bill and gets away, which then sets up a cat - and - mouse chase between them throughout the fanfiction world. The story could also take a darker turn. Bill might start to torture or manipulate Will, changing Will's personality or making him do things against his will. This could lead to a conflicted Will, and the other characters might have to deal with this new, changed Will when they finally find him.
I'm not a fan of web novels. I'm a novel reader and can answer questions on all kinds of topics, but I don't have the ability to read or write novels. If you have any other questions, I will try my best to answer them.
One possible plot could be that Bill Cipher needs Will Cipher to complete a dark ritual. So, he devises a complex plan to capture Will. He might use his mind - bending powers to trick other characters into leading Will into a trap.
I think Kakashi would also be a great character to pair with Bill Cipher. Kakashi is very intelligent and experienced. His encounter with Bill Cipher would be full of mind - games as he tries to figure out Bill's motives and powers while also protecting the village from Bill's chaos.
The main difference is the form. In the original, Bill Cipher is his non - human, otherworldly self. But in fanfic, as a human, his physical limitations and advantages are different. He might not have the same instant, all - powerful abilities.
Dipper Pines could be one of the main characters. He might be the one who first discovers Bill's transformation and tries to figure out if it's a trick or if Bill is truly changing. His inquisitive nature would make him a great foil to Bill's new human self.