I'm not sure specifically as 'apollyon novel' could refer to various things. It might be a very niche or self - published work that I'm not familiar with.
It depends on the source. If the book is in the public domain, like if the copyright has expired, then it is legal to read it for free from a legitimate source. For example, on Project Gutenberg which specializes in public domain works.
One idea could be to have Apollyon cross over into a different time period within the For Honor universe. Maybe she finds herself in a more peaceful era and has to decide whether to disrupt it or adapt. Another could be a crossover with a character from another game where she has to battle for supremacy in a new and unfamiliar land.
Some websites like ManyBooks also provide free e - books. It's possible that 'Apollyon' could be found there. However, make sure to check the legality of the source. Piracy is not acceptable. You can also look for fan - made websites dedicated to sharing free literature, but be cautious as some might not be legal or reliable.
First, know your characters well. For Apollyon, understand her motives, her backstory, and her personality traits. Then, when creating the crossover, make sure the two elements blend well. If it's a crossover with another game, find common themes like combat or honor. Also, create a strong plot. Maybe start with a conflict that draws Apollyon into the crossover situation.