The theme of sacrifice also appears frequently. Given their selfless natures, fanfics may show situations where either Saber or Shirou has to sacrifice something for the other or for the greater good, which adds a lot of emotional depth to the stories.
Love and devotion are very common. Since their relationship in the original work is so complex and deep, fanfics often explore how their love for each other can overcome different obstacles.
A popular one is 'Saber and Shirou's Parallel Adventure'. In this, the author takes a creative turn and puts them in a parallel universe where they have different roles but still find their way back to each other. It has a great mix of action and romance that keeps readers hooked.
The theme of sacrifice also often appears. Shirou is known for his self - sacrificing nature, and in fanfics, this can be explored further in relation to Saber. For instance, how his willingness to sacrifice himself affects Saber and how she might respond to it, either trying to prevent it or being inspired by it.
One common theme is love. Their relationship is often explored in different ways, from a slow - burn romance to an instant connection. Another theme is loyalty. They are both loyal characters, and in fanfiction, this loyalty is often tested and reaffirmed.
One common theme is redemption. Given Kiritsugu's complex past, many fanfics explore his journey towards redeeming himself in the context of the Beast Lair.
One common theme is sacrifice. Shirou is often willing to sacrifice himself for Saber, and vice versa. It shows the depth of their love.
Growth is also a prevalent theme. Both characters grow as individuals within their marriage. Shirou might become more confident and assertive, while Saber may learn to be more open and emotional. This is often shown through various events in their married life in the fanfiction, like dealing with financial issues or making big decisions together.
Some Beast Lair Fate fanfics are known for their unique takes on the magic system. They might expand on how the magic works, introduce new types of spells or magical artifacts. A great fanfic could be one where a previously unknown mage family is introduced, and they have a distinct way of using magic that affects the course of the Grail War. Fanfics can also play with the concept of time travel within the Fate universe, allowing characters to interact with different versions of themselves or change past events in interesting ways.
Growth is another theme. Both Shirou and the harem members usually experience personal growth. Shirou might become more confident in handling relationships, while the others could grow in their skills or understanding of themselves. For example, a character in the harem could start as shy but become more assertive over time. This growth is often intertwined with the development of their relationships.
The idea of sacrifice also pops up a lot. Given the nature of the Fate series, the characters may be in situations where they have to sacrifice for one another. In fanfics, this can be explored in different ways, like Saber sacrificing her power to protect Rin and Shirou.
Another theme could be redemption. Maybe Shirou as a Dead Apostle is seeking redemption through his relationship with Saber. And Saber might be trying to save him from his dark path. It's also common to see themes of forbidden love, as their natures seem so different that their relationship might be seen as something not allowed in the normal Fate world order.