his true mate

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 a new character entirely. Maybe a hybrid of some sort, half - vampire and half - werewolf, which would be a very unique and interesting choice for her true mate. This would bring a whole new set of dynamics to the story as Bella has only been involved with either vampires or werewolves before.

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.

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.

Yes, there are quite a few. You can start by looking on fanfiction platforms like Archive of Our Own. Some stories might explore an alternate universe where Harry and Lucius have an unexpected bond, perhaps in a world where the lines between good and evil are more blurred. It often involves complex character development and unique plot twists.

I'm not sure specifically what this 'free his invisible mate story' is about without more context. It could be a very unique, perhaps fictional or symbolic story where someone is trying to free a mate that is invisible, which might be metaphorical for freeing someone from a hidden or unacknowledged state.

They could have an adventure exploring the various regions of Middle - Earth. Maybe they go on a quest to find a lost magical artifact that has the power to bridge the gap between the Harry Potter world and Middle - Earth.

In a lot of these fanfictions, Harry Potter himself could be the one who is Hermione's mate. This often changes the whole dynamic of the original friendship triangle in the Harry Potter series. It allows for new storylines to be explored, such as how their relationship affects their fight against Voldemort.