A great fanfic is 'Beyond the Shadow's Veil'. In this one, the story explores what lies beyond the typical scope of the Eminence in Shadow's activities. It has a great plot that keeps you hooked as it reveals secrets and new aspects of the shadowy world.
You can start by looking on popular fanfic websites like Archive of Our Own or FanFiction.net. Just search for 'Eminence in Shadow reaction fanfic' in their search bars.
One interesting concept could be the exploration of different characters' backstories that might not be fully delved into in the original work. For example, how a minor character in the official story gets a more in - depth arc in the fanfiction.
Another interesting concept is to create an alternate universe where the power dynamics are completely different. Maybe the shadow organization is the ruling power, and the story focuses on how the world adapts to that. It could also involve the main character having to deal with different challenges in this new setup.
One interesting concept could be exploring different backstories for the characters. For example, delving deeper into the past of Cid Kagenou before he became 'The Eminence in Shadow'. Another concept might be alternate universes where the power dynamics or relationships are different.
Some MLP reaction fanfics focus on the ponies reacting to a change in the seasons that is more extreme than usual. For instance, if winter comes with a massive blizzard, Applejack would be worried about the orchard but also determined to protect it. Rarity, on the other hand, might be initially concerned about how the cold will affect her fur and her fashion but then find creative ways to stay warm and stylish.
A great 'God of War' reaction fanfic might explore the reaction of Atreus to his father's past deeds as they are gradually revealed. He could be shocked, angry, or even more determined to make amends for his father's wrongs. Also, fanfics could show the reaction of the enemies when they face a more strategic and less brutal Kratos. They might underestimate him at first, thinking he's lost his edge, but then quickly realize he's still a formidable foe.
Some fanfics focus on the reactions of ordinary civilians during WW2. They might show how a family copes with the rationing, air raids, and the general fear that pervaded the time. By writing from the perspective of these civilians, the fanfic can give a very human and relatable view of the war.
One plot idea could be that Rose discovers Cid's true power in a moment of crisis. For example, when facing a powerful enemy that the Shadow Garden can't easily defeat, Cid reveals his real capabilities to save Rose and the others. Another idea is a love triangle where Rose has feelings for Cid, but Cid is so focused on his shadowy plans that he doesn't notice at first, while another character also vies for Rose's attention.
The world - building in the novel is quite engaging. It presents a fantasy world with different power systems and factions. The way the author describes the various magic and combat abilities adds depth to the story. Also, the relationships between the characters, especially how they interact with the protagonist's 'shadow' persona, are complex and full of surprises.
The unique concept is really interesting. The main character has this delusion of being a mastermind behind the scenes, which creates a lot of comical and unexpected situations. For example, he thinks he's pulling all the strings while others are just going about their normal lives, not realizing his 'grand plans'.