One common theme is the exploration of Shalltear's power. Since she's a very powerful character in the Overlord universe, many fanfictions like to test her limits when she's in a crossover situation. Another theme is loyalty. Shalltear's loyalty to Ainz is a big part of her character, and in crossovers, this loyalty often gets challenged or reaffirmed in different ways. For example, in some crossovers, she has to choose between following Ainz's commands and doing what she believes is right in the new world she's in.
Arche is a character with a strong sense of justice. She is intelligent and has her own beliefs. Shalltear, on the other hand, is a powerful vampire. In the web novel, their existence adds a lot of color to the story.
The location of the Shalltear fight in the Overlord novel is quite specific and tied to the story's plot progression. You'd need to delve into the specific chapters to get the exact details.
Another theme is loyalty. Some fanfictions focus on whether the OC can earn Shalltear's loyalty or vice versa. This can lead to complex relationships and interesting plot developments as they face various challenges together. And often there are themes related to the dark and somewhat cruel nature of the Overlord world, which both the OC and Shalltear are part of.
Sure. One interesting 'Overlord Shalltear crossover fanfiction' is 'Shalltear in Another World'. It takes Shalltear and drops her into a different fantasy setting, exploring how she adapts with her unique powers and personality. Another one could be 'Shalltear's Adventure Beyond Nazarick', where she embarks on a journey outside of her familiar domain and encounters various new challenges and characters.
In the Overlord web novel, Arche might initially be wary of Shalltear due to her being a powerful and somewhat menacing vampire. As the story progresses, depending on the plot twists, their relationship could potentially shift. Maybe they could find some common ground in certain situations, or perhaps their differences could be exploited by other characters. Their relationship development is an interesting aspect that adds depth to the overall story.
There's also 'The Unlikely Alliance' which features an OC who teams up with Shalltear in some unexpected adventures. It shows great character development for both the OC and Shalltear, and the plot twists keep the readers engaged throughout the story.
There's Demiurge. He is a very intelligent demon and his plans and strategies often cross paths with Shalltear's activities. Also, Sebas Tian, although his role might be more on the periphery in relation to Shalltear, but he is still an important part of the Nazarick community which is the backdrop of the 'Shalltear Bloodfallen' light novel.