A common theme is the exploration of their individual insecurities within the context of their relationship. Soldier 76 may be insecure about his past actions and how they are perceived, while Sombra may be insecure about her place in the world. Their relationship in the fanfiction can be a way for them to overcome these insecurities. Also, the theme of sacrifice often comes up. They might be put in situations where they have to sacrifice something for the sake of the other or for the greater good, which adds depth to their relationship.
Another theme is the discovery of self - worth. Sombra might start to see her value differently when she's around the Radiant. For example, in some stories, she realizes she can use her skills for good instead of just her own gain. This theme is explored through her interactions with the Radiant members.
One common theme is the idea of redemption. Sombra, often seen as a more morally ambiguous character, may find redemption through her relationship with the more heroic Tracer. Another theme is trust. Since they are from different backgrounds, building trust between them is often explored. For example, in many fanfictions, Sombra has to prove herself to Tracer.
Another theme is the idea of redemption or change. Sombra might be seen as a character who could help Symmetra break out of her very strict ways, or Symmetra could be the one to make Sombra more responsible. It's about how they influence each other's growth.
A frequent theme is the exploration of their different backgrounds. Sombra coming from a more shadowy, underworld - like background and Bridgette from a more traditional hero - making place. Their relationship in fanfiction might be about bridging those two worlds. Also, trust is a big theme. Since Sombra has a reputation for being sneaky, stories often revolve around whether Bridgette can trust her and how that trust develops or breaks down.
Well, themes like forbidden love are quite common. Since King Sombra may be an 'outsider' or a 'bad guy' in the original context, a relationship with an OC can be seen as something not allowed. Also, themes of discovery are there. The OC might discover secrets about King Sombra or vice versa, which drives the story forward. And then there's the theme of transformation, where either the OC or King Sombra changes because of their interaction.
One common theme is the idea of a secret relationship. Since both characters have rather mysterious and shadowy aspects to their personalities in the game, it makes sense that their relationship in fanfiction would often be hidden from others. For example, they might meet in secret locations within the Overwatch universe.
One common theme is the power struggle. Given Celestia's role as a powerful ruler of light and Sombra's association with darkness and power, many fanfics explore how they deal with their different levels of power. For example, in some, they have to find a balance between their powers to achieve a common goal.
One common theme is the contrast between their personalities. Sombra is mysterious and cunning, while McCree is more of a straightforward cowboy type. Their differences often lead to interesting interactions and relationship dynamics. Another theme is the idea of trust. Since they come from different sides in the game's lore, building trust is a big part of their relationship in many fanfics.
One common theme is the power of change. King Sombra is often portrayed as a villain, but in these fanfictions, through his relationship with Twilight Sparkle, he can change for the better. Another theme is the exploration of the unknown. Their relationship is not a typical one in the Equestria lore, so it allows for a lot of exploration into uncharted territory.
One common theme is power struggle. King Sombra is a powerful and often menacing character, and Twilight is also very powerful in her own right. So, their interactions can be centered around who has more power or how they can use their powers against each other.