It could be Hermione. In some alternate interpretations, there could be a situation where Hermione, while trying out a new and powerful magic, accidentally hurts Harry. Their friendship is put to the test as Harry has to deal with the pain and Hermione has to come to terms with what she's done.
Maybe it's Ron. Suppose Ron gets jealous of Harry's fame and power and, in a moment of weakness and envy, decides to abandon Harry to die. This would create a lot of drama as Ron and Harry have been friends for a long time, and such a betrayal would be a huge shock to the story's readers.
It could be the Death Eaters. Even if they are on the 'bad side', they might see an opportunity to disrupt Harry's life and weaken him. By forcing him to reject his mate, they can create emotional turmoil for Harry, which would make him less focused on fighting against them.
This type of fanfiction often dives into the psychological aspects of the characters. The kidnapped mate may experience a range of emotions such as fear, anger, and confusion at first. As the story progresses, they might start to see Klaus in a different light. The writer could also introduce other characters who react to this situation, either trying to rescue the mate or siding with Klaus, which adds more layers to the story.
There could be multiple novels titled 'the forsaken novel' by different authors. It could be a self - published work by an indie author, or a relatively unknown book written by someone who hasn't gained wide recognition yet. Without further details, we can't identify the author.
I'm not sure specifically as there could be many novels with that name. It might be about characters who are forsaken or abandoned in some way, perhaps in a post - apocalyptic world or a society where they are outcasts.
One possible reason could be some sort of external threat. Maybe there's a dark force that wants to use his mate against him, so to protect her, he's forced to reject her. For example, if there are dark wizards who plan to capture his mate and use her as a bait to get to Harry, he might think rejecting her would keep her out of danger.