Perhaps it was a weapon created by a rogue ninja with unique powers. And for some reason, it found its way to Naruto in Wave. It might also be a weapon that was enchanted by a sorcerer long ago and has special abilities that Naruto will discover as he uses it.
The scythe might make Naruto's combat style more aggressive. He could use it for long - range attacks and quick slashes, adding a new dimension to his fighting. For example, he could combine his shadow clone jutsu with scythe attacks, having clones distract the enemy while he swoops in with the scythe.
He might start using more sweeping and slashing motions. Instead of his usual close - range punches and kicks, he could use the scythe's long reach to keep his opponents at a distance. For example, he could swing the scythe in wide arcs to fend off multiple enemies at once.
One potential character could be Sasuke. Imagine in a dark, alternate universe fanfic where Sasuke, instead of using his sword, wields a scythe. It could be a symbol of his more menacing and reclusive nature. He might use it with his Sharingan abilities, making his strikes not only powerful but also unpredictable as he can anticipate his opponents' moves.
He might use a scythe with a chakra - infused blade. This would give it an extra edge (literally) in combat, allowing it to cut through tougher materials. The scythe could also have some sort of sealing mechanism on it, similar to his kunai, so he could store small items or even chakra - based attacks within it for surprise strikes.
The origin could be some ancient, long - forgotten magic. Maybe it was created by a powerful and now - extinct clan. They might have imbued it with a spirit or some form of intelligence for a specific purpose, like protecting a hidden treasure or an important location.
Well, he might incorporate more acrobatic moves. The scythe is a large and unwieldy weapon compared to his usual ninja tools. So he'd probably have to be more fluid in his motions, using spins and wide arcs to attack. He could also use his ninja skills like chakra control to enhance the power of his scythe strikes, for example, coating the blade with chakra for a stronger cut.
One possibility is that the scythe is a key element in a prophecy. Naruto, as the main character, is fated to find it. With this scythe, he could gain new allies who are also interested in its power. However, he would also face new enemies who want to take the scythe from him. This would create a lot of tension and action in the fanfiction.
You can start by looking on popular fanfiction websites like Archive of Our Own (AO3). It has a large collection of RWBY - related fanfictions, so there's a good chance you'll find some Ruby Gets a Better Scythe stories there. Just use the search function and type in the relevant keywords.
One great story could be where Ruby discovers an ancient technique to upgrade her scythe. This might involve her going on a quest to find rare materials and learning from an old, wise blacksmith. In this fanfiction, the author could describe in detail how Ruby hones her skills with the new and improved scythe, making her even more formidable in battles.