A common theme is power - seeking. They are often depicted as constantly striving for more power and ruling over the universe. Another theme is their unique bond, whether it's a friendship or a more sinister partnership.
The Saiyans could also be antagonists. If they discover Black Goku's true nature and his alliance with Zamasu, they would likely oppose them to protect their race and the universe.
One idea could be that they discover a new realm together and have to face an unknown threat there. Their combined power might be put to the test in ways they never expected.
One popular 'goku black x zamasu fanfiction' is 'The Dark Alliance'. It delves deep into their partnership and the chaos they create in the universe. Another interesting one could be 'The Merged Power', which explores what would happen if they combined their powers in different ways.
A common theme is power and corruption. Since both characters are power - hungry in different ways, many fanfictions explore how their thirst for power corrupts them further. For example, they might go on a rampage across different universes to gain more power.
One popular 'goku black and zamasu fanfiction' is 'The Dark Ascension'. It delves deep into an alternate universe where Goku Black and Zamasu's plans reach even more terrifying heights. Another great one is 'Fusion of Darkness' which explores a scenario where they manage to fuse in a different way than in the original story.
In the manga, Goku managed to kill Zamasu by combining his strength with Vegeta and performing a joint attack. They also exploited Zamasu's weaknesses to gain the upper hand.
A good exploration of their personalities is key. Since they both have distinct traits, seeing how they interact based on who they are is important. For example, Zamasu's self - righteousness and Black's more primal power.
There's also 'Zamasu and Black: A Forbidden Bond'. This fanfiction focuses on the more emotional side of their relationship. It shows how they might have come to understand each other on a deeper level, despite their differences. It's really well - written and the characterizations are on point.
Character development is also crucial. In many such fanfictions, Female Goku Black may start as a villainous or at least antagonistic character. But as the story unfolds, she might change due to her interactions with Goku. This transformation can be really interesting to follow. For example, she could start to question her own motives or even develop feelings for Goku, which is a big shift from her initial stance.