There's a fanfic called 'Fire God Slayer in the Land of Fire'. This one focuses more on the cultural aspect. The character with Fire God Slayer abilities tries to understand the difference between their own magic and the ninja's use of fire techniques. It has a great plot where they interact with various ninja clans and learn about the history of the Land of Fire in relation to fire - based powers.
I've read 'Naruto: Fire God Slayer's Ascent'. It's an interesting take. In this fanfic, the Fire God Slayer abilities are used to enhance Naruto's own fire - based jutsu. It has some really cool fight scenes where the combination of Naruto's normal ninja skills and the Fire God Slayer powers are shown off. It also delves into how the ninja world reacts to this new kind of power.
One good Naruto Gravity Dragon Slayer fanfic could be 'Naruto: Dragon's Ascent'. It combines the unique powers of a Gravity Dragon Slayer into the Naruto universe in a really interesting way. The story has Naruto learning new skills related to gravity manipulation, which gives a fresh twist to his character development.
They often introduce new characters or give existing characters new abilities. It allows for different character development arcs. A fanfic might have Sasuke gain some Fire God Slayer abilities and see how that changes his relationship with Naruto and his own goals. This changes the dynamics of the story and makes it fresh compared to the original Naruto storyline.
I'm not sure if it's popular. There are so many Naruto fanfics out there, and it's hard to say which ones are popular without checking fanfic platforms and their rankings.
There's a fanfic called 'Alliances Beyond Worlds'. In this, the main characters from each series form an alliance to face a common threat that endangers all three of their universes. It's really interesting to see how the different fighting styles and magic/powers interact. For instance, the Demon Slayer's breathing techniques blend with Fairy Tail's magic in unexpected ways.
One interesting 'naruto crossover fire emblem fanfic' could be the one where Naruto characters are dropped into the Fire Emblem world and have to adapt to its combat and political systems. It makes for a really unique read as you see Naruto's ninjutsu blend with Fire Emblem's magic and weapon - based combat.
I'm not sure specifically as I haven't read this fanfic in detail. But generally, it might be about Naruto having god - like powers and being involved in scenarios related to a God Slayer concept, perhaps fighting against gods or having abilities on a divine level within the context of the fan - created story.
Sasuke could be a great main character. Given his natural affinity for fire - based jutsu in the Naruto series, the addition of Fire God Slayer powers could make him even more formidable. He could use these new powers to seek revenge in a different way or to protect the village in a more powerful capacity.
A plot could involve a Fire God Slayer from another dimension accidentally ending up in the Naruto world. This character then has to find a way back home while also getting involved in the local politics and power struggles. They might use their Fire God Slayer powers to help the oppressed in the ninja villages, creating both allies and enemies along the way.
You could start by creating a character who is from a far - off land where the Sky God Slayer powers are known. This character arrives in the Naruto world and has to adapt to its different rules and cultures while still using their powers. For example, they might have to learn how to use their powers without disrupting the chakra system that is so fundamental in Naruto.
There are probably some out there. A lot of fanfic writers are inspired by the idea of Lucy and a fire dragon slayer. You might have to dig around a bit, though. Sometimes it depends on how popular the pairing or concept is within the fandom at the time. Some of the stories could be about Lucy teaming up with a fire dragon slayer on an adventure, or there could be a more romantic take on their relationship.