It could be really interesting. Maybe Harry would create a noble phantasm that has the power of his Patronus. Since his Patronus is a stag, the noble phantasm could be a powerful stag - like entity that can charge at enemies and protect those he cares about. It might also incorporate elements of his Gryffindor courage, being unyielding in the face of danger.
Hippogriffs could be involved. They are majestic and powerful creatures. Harry might incorporate the loyalty and strength of a Hippogriff into his noble phantasm. It could have the ability to fly at great speeds and attack enemies with its sharp beak and talons.
In fanfiction, Noble Phantasm can enhance 'Harry Potter' by introducing new types of magic battles. Instead of just using regular spells, characters could use the special abilities of Noble Phantasms. This could change the dynamics of duels and battles, making them more exciting and unpredictable. For instance, if a character's cloak of invisibility was a Noble Phantasm, it might have the power to make the wearer completely undetectable by any magical means, including dark magic detectors.
There might be a fanfiction where the Gryffindor sword is turned into a Noble Phantasm. In this story, the sword could have the ability to cut through any dark magic, not just physical objects. It could be a key weapon against a new and powerful dark wizard that the characters in the fanfiction face, and it might have some sort of sentience, guiding Harry and his friends in their battles.
Naruto's determination could be a key part of his Noble Phantasm. For example, his Noble Phantasm could be a cloak of unwavering resolve that makes him immune to mental attacks and boosts his physical abilities when he is facing extreme odds.
In Harry Potter fanfic, the ancient and noble houses often play crucial roles. For example, the Malfoy family from House Malfoy. They are known for their pure - blood supremacist beliefs. Their manor is a symbol of their wealth and status. These houses add depth to the wizarding world, creating complex family dynamics and power struggles.
They are significant as they represent tradition. For example, the pure - blood houses have certain etiquettes and magic that has been passed down for centuries.
Unsettling plot twists can contribute to a fanfic being a 'nightmare' type. For example, if it turns out that Dumbledore was actually an evil mastermind all along and has been manipulating Harry for his own dark purposes. Or if the prophecy was a lie and Harry's whole life has been a cruel joke. These kinds of revelations that shatter our perception of the original story can make a fanfic feel like a nightmare.
One interesting aspect could be the unique combination of Shirou's character from one universe with the RWBY setting. It might lead to new and unexpected power combinations. For example, how his Noble Phantasm abilities would interact with the Grimm in RWBY. Another aspect could be the exploration of Shirou's character in a different context, perhaps showing different sides of his personality as he adapts to the RWBY world.
One idea could be Naruto obtaining a Noble Phantasm that is related to his Rasengan. Maybe it's a super - powered Rasengan - based weapon that can only be summoned in times of great need. It could have the power to defeat powerful enemies with a single blast.