Well, perhaps Hermione and Klaus meet in a dream - like state first, as a premonition of their mate bond. When they finally meet in person, there is an instant attraction and connection. But Hermione is hesitant because of Klaus's reputation. So, Klaus has to prove himself worthy of her. They could then embark on a journey to break a curse that is related to their mate bond, facing various challenges along the way, like dark magic and ancient creatures.
A possible plot is that Hermione and Snape are forced to keep their relationship a secret at first. As Hermione adjusts to her new life as a vampire, she discovers that there are ancient vampire laws that could put Snape in danger if their relationship is revealed. They must navigate through these laws while also dealing with their feelings for each other. Snape might use his skills in potions to create something that helps Hermione cope with the difficulties of being a vampire, like a potion that lessens the pain of sunlight exposure.
A plot could revolve around Hermione being kidnapped by Greyback's pack. But instead of succumbing to fear, she uses her intelligence to gain the respect of some of the werewolves. Greyback is initially hostile but gradually becomes intrigued by her. Their relationship could then develop as Hermione tries to broker peace between the werewolves and the wizarding community. Maybe there's a prophecy involved that says only their union can bring peace, and they have to navigate the complex emotions and politics around it.
A plot could involve a magical accident that causes Hermione and Charlie to swap some of their magical abilities. They have to work closely together to reverse the spell. During this time, they learn about each other's strengths and weaknesses and develop feelings for one another.
One interesting Klaus Mikaelson mate fanfiction could be 'The Bond Beyond Time'. It delves into the idea of a mate from a different era finding their way to Klaus. Another might be 'Mate Against All Odds' which focuses on a mate who has to face numerous challenges in the vampire - werewolf - witch world of Klaus Mikaelson. And 'Klaus's Hidden Mate' where the mate is initially hidden from Klaus due to some dark magic.
There could be a Klaus Mate OC fanfiction where the OC is from a different time period. Maybe she's a time - traveling witch who accidentally lands in Klaus' era. Their relationship starts off rocky as Klaus is suspicious of her motives, but over time, they develop a deep bond as she helps him with some of his problems in the supernatural world.
One idea could be the demon's mate having a special power that is the key to saving the demon realm from an ancient curse. Another could be the struggle of the mate to adapt to the demon's dark and dangerous world while still holding onto their own humanity. Maybe the demon's mate is from a different supernatural species, like an angel, and their relationship is a forbidden love that defies the rules of both their worlds.
The baby could also have a special connection to the spirit world. Bonnie, with her witch powers, and Klaus, with his long and complex history, could find themselves on a journey to understand this connection. They might meet different spirits who either offer guidance or pose a danger to the baby as it grows up.
One idea could be that Klaus and Caroline are in a relationship, but Camille's presence causes some jealousy and tension. For example, Camille might still have some unresolved feelings for Klaus, and Caroline has to deal with that while also trying to strengthen her bond with Klaus.
One idea could be them navigating the supernatural politics together as a married couple. Klaus' power and Caroline's determination would make for an interesting dynamic in dealing with other supernatural beings.
Perhaps a plot where Hope gets lost in a time - warp and Klaus has to travel through different eras to find her. Along the way, he discovers new things about their family's past and how it relates to Hope's future. This could involve them meeting their ancestors and learning from their experiences.