One interesting crossover could be the political intrigue. In 'Game of Thrones', the power struggles between different houses are intense. In the Roman Empire, there were also power struggles among senators and the imperial family. So, a fanfiction could explore how the political tactics from one world would play out in the other. For example, the Roman concept of patron - client relationships might be applied to the relationships between lords and vassals in Westeros.
Well, it could be a story where the values of the Roman Empire, such as honor and loyalty in the military, are introduced to the characters in 'Game of Thrones'. Maybe a character from the Seven Kingdoms travels to a land inspired by the Roman Empire and brings back new ideas. Or perhaps there are gladiator - like battles in the arenas of Westeros, with characters from both worlds competing for glory. It would be a wild mix of the two universes.
One idea could be a story where the political intrigue of the Roman Senate is mirrored in the power struggles of the Great Houses in Westeros. For example, the patrician families in Rome could be compared to the noble houses in Game of Thrones, with similar backstabbing and alliances for power.
A possible main character could be a Westerosi noble who is intrigued by the Roman Empire and decides to journey there. He could be like Tyrion Lannister, smart and cunning, trying to navigate the new and strange world of the Romans. Another could be a Roman general who finds himself in Westeros and has to adapt to its different rules of war and power.
You could combine characters by having a Roman character end up in Westeros. For example, a Roman centurion could be transported to Westeros and find himself in the middle of the War of the Five Kings. He could use his military training to fight for one of the sides or try to find a way back home.
The common people from the Roman Empire would face a lot of difficulties. The harsh winters, the constant threat of war, and the feudal system in Westeros are very different from what they are used to. But some might be able to use their skills in farming, building, or trading to carve out a living in this new and dangerous land.
One key element is the political intrigue. Just like in the original series, a good fanfiction will have houses vying for power, backstabbing, and forming alliances. For example, a story might show how a minor house tries to rise to power by playing the major houses against each other.
Jon Snow is often very popular. His mysterious parentage and his sense of honor make him a great character to explore further in fanfiction. Writers can expand on his time beyond the Wall, or his relationships with other characters like Daenerys in new and interesting ways.
Perhaps a 'Game of Thrones Roman Fanfiction' could involve a character from Rome being magically transported to Westeros. This Roman could introduce new ideas such as Roman architecture, building great amphitheaters in the Seven Kingdoms. They could also bring their religious beliefs and clash or blend with the existing faiths in Westeros. This would create a whole new dynamic of cultural exchange and conflict within the world of Game of Thrones.
First, study the characteristics of both. The Roman Legion had strict formations and strategies. In a fanfic, you could make a legionnaire the main character. He could be thrust into the chaos of Westeros, with its different houses vying for the Iron Throne. Maybe he uses his Roman military knowledge to train a group of outcasts into a formidable force. This new force could then play a role in the power balance, similar to how the Unsullied did in the original series.