One interesting concept could be the exploration of how the Holy Grail's magic might interact with the existing magic in the Harry Potter universe. For example, it could be a source of power that Voldemort tries to obtain, leading to a whole new series of battles and plot twists.
Another concept could be that the Holy Grail has the power to change the rules of magic. It could give wizards the ability to perform magic without wands, or even bring back the dead. This would completely disrupt the established order in the Harry Potter world and lead to a lot of moral and ethical dilemmas for the characters to face.
One interesting concept is alternative Servant summonings. For example, seeing a different class for a well - known character like if King Arthur was summoned as a Caster instead of a Saber. Another concept could be different Masters, perhaps a non - traditional or more morally ambiguous Master. And then there are the alternate storylines that might change the location or rules of the Holy Grail War.
One interesting concept could be summoning servants from different time periods and seeing how they interact with the DxD universe. For example, a servant from ancient Greece might have a unique perspective on the devils and angels in DxD. Another concept could be a servant with special powers that are not typically seen in the original series, like a servant who can manipulate time in a different way than what's shown in DxD. Also, the idea of a servant having a secret mission that ties into the overarching plot of DxD could make for an engaging fanfiction.
One interesting concept could be new Servant classes. Maybe there are unique combinations of skills and abilities that are different from the original classes in the regular Fate series. For example, a Servant with a blend of Assassin and Caster abilities, which would make for very stealthy and magically powerful combat strategies.
One interesting concept could be exploring more about the Marauders' time at Hogwarts. Fanfiction might expand on their adventures, like pranks they played that were never mentioned in the original book. Another could be different interpretations of Sirius Black's escape and his relationship with Harry during that time.
Some fanfictions in Harry Potter 2 might play with the idea of the basilisk having different powers or weaknesses. It could also explore the idea of a hidden connection between Ginny and the Chamber of Secrets that goes beyond what was in the original story. There might be fanfictions that change the role of certain characters, like making Neville a more central figure in solving the mystery of the Chamber.
The Holy Grail can tip the power balance. If a character like Dumbledore got hold of it, he could potentially become even more powerful and better able to protect Hogwarts and the wizarding world from dark forces. His already great magical abilities could be enhanced, making him an even greater force against Voldemort.
One idea could be introducing a new type of Servant, like a Servant from a different mythology not previously seen in the Grail Wars. This would bring in new powers and dynamics. Another could be having a master who is an ordinary person thrust into the war by accident and has to quickly learn the ropes. For example, a school student who stumbles upon the Grail War's secrets and has to fight to survive.
The Legend of the Holy Grail had many options. One of the recommended novels was " The 100-fold Cultivation System Instantly Upgrades to 999 ". This novel described how the protagonist, Jiang Chen, obtained the 100-fold Cultivation System after crossing over to another world and became stronger through continuous upgrades. In addition, there was also the novel " Naruto Holy Grail System ". After the protagonist passed through the Naruto World, he obtained the Holy Grail System and used the Holy Grail Space to infinitely strengthen and increase his attributes. These two novels are about the legend of the Holy Grail. They can satisfy your reading needs.
One interesting concept could be exploring new magical creatures in the Harry Potter kingdom. Maybe there are some hidden species that haven't been discovered in the original series. Another could be alternative forms of magic that are unique to the fanfiction's version of the kingdom. And also, new relationships between different houses or characters can be quite fascinating.
One interesting concept could be the use of magic in relation to physical laws. For example, how spells might interact with gravity. Maybe a levitation spell actually counteracts the force of gravity in a way that can be explained through some made - up 'physics' in the fanfiction.