You can start by looking on fanfiction websites like FanFiction.net or Archive of Our Own (AO3). These platforms have a vast collection of fanfic stories, and you can simply search for 'Severus and Hermione Christmas' in their search bars. There might also be some dedicated Harry Potter fanfic communities where fans share and discuss such stories.
The allure also lies in the fact that it's a bit of a forbidden or unexpected pairing. In the context of the Harry Potter series, Severus has a complex relationship with Hermione's friends, especially Harry. So, seeing them in a Christmas story, perhaps sharing a moment under the mistletoe or exchanging gifts, goes against the norm and creates a sense of intrigue. It gives fans a chance to see the characters in a new light and explore different emotional and relationship dynamics.
One popular trope is the 'enemies to lovers' where Severus initially dislikes Hermione but gradually falls for her. Another is the 'teacher - student relationship' dynamic which adds an element of forbidden love. And the 'redemption arc' for Severus through his relationship with Hermione is also common.
Family and belonging are also common themes. Even though Severus has a rather solitary life, in Christmas fanfics, he might experience a sense of family, whether it's with his colleagues at Hogwarts or some unexpected characters. It could be about him finally feeling like he belongs somewhere during this festive time.
Another way Severus could save Hermione is by using his knowledge of the Dark Arts in a positive way. If she was hurt by a Dark spell from Ron (in the context of the fanfic), Severus might be able to counteract the spell's effects. He has extensive experience with Dark Arts spells, so he could figure out what spell Ron used and then use a counter - spell to reverse the damage.
Another interesting one is 'Towards an Understanding'. Here, Hermione runs to Severus after having a falling - out with her friends. Severus, initially reluctant, gradually becomes a mentor - like figure to her. It beautifully portrays their character development and how they learn from each other.
There could potentially be a Severus Snape mpreg by Hermione fanfic out there. The world of fanfiction is huge and full of all kinds of creative and sometimes out - of - the - ordinary ideas. However, many mainstream fanfic platforms might not allow such content if it goes against their rules regarding appropriate or acceptable storylines. You might have to search in more specialized or lenient fanfic communities to find it, if it exists at all.
Often, there's a theme of the unexpected. Their relationship in fanfic is usually not what one would expect given their roles in the original books. Also, the theme of mentorship can be found. Hermione might learn from Severus' deep knowledge of magic, and he could learn from her modern - thinking. There's also the theme of hidden feelings, as they initially seem at odds but may have deeper, unspoken emotions for each other.
There's also 'Severus Snape's Christmas Miracle'. In this story, Severus discovers the true meaning of Christmas through an unexpected encounter. It delves deep into his character, showing his softer side during the holiday. The author does an excellent job of creating a believable scenario within the Harry Potter universe.
One great 'Lucius Hermione Severus fanfic' is 'The Unlikely Trio'. It explores the unique dynamic between the three characters in a magical adventure setting. Another is 'Bonds Beyond Expectations' which delves deep into their relationships and how they overcome differences in a Hogwarts - like world. And 'A Different Sort of Alliance' is also interesting as it shows how they come together for a common goal against a dark force.