Fanfiction.net also has a good number of such fanfics. However, you need to be a bit more patient while searching as the interface might not be as user - friendly as AO3. But it's still worth checking out as there are some hidden gems there.
There are quite a few good ones out there. You can start by looking on popular fanfic platforms like Archive of Our Own. Some fanfics might focus on unique storylines involving the relationships between the OC, Jean Grey, and Emma Frost. For example, a story could be about an OC who has special powers and gets caught in the middle of the complex relationship between Jean and Emma, leading to a series of adventures and self - discovery.
One common theme is the power struggle between them. Given their powerful psychic abilities, they often clash or compete in fanfictions. Another theme is friendship. Some stories explore how they could put aside their differences and become friends. And of course, there's the theme of rivalry for the affections of other characters, like Cyclops for example.
One common theme is the discovery of self. The OC often goes through a journey of self - discovery while interacting with Jean Grey. For example, they might learn about their own powers or their place in the world because of their relationship with her.
One major theme is the struggle between the OC's normal life and the extraordinary world of mutants that Jean Grey represents. Also, themes of acceptance are quite common. The OC may face discrimination, and Jean Grey helps them through it. For example, in some fanfics, the OC is a mutant with a very visible mutation, and Jean Grey uses her telepathy to help the OC accept themselves. It can be a very emotional and relatable theme. There are also fanfics that revolve around the theme of sacrifice, where either the OC or Jean Grey has to make a difficult choice to save the other or the entire mutant community.
I really liked 'A New Perspective'. In this fanfic, the OC brings a fresh outlook to the X - Men universe, especially in relation to Jean Grey. It has some really interesting plot twists and character developments. The way the author portrays the connection between the OC and Jean is both engaging and thought - provoking.
One possible plot could be that the OC is a new mutant who arrives at the X - Men school. Jean Grey senses a powerful and unique energy within the OC. Scott is initially cautious but as they all train together, the OC starts to develop feelings for both Jean and Scott. Meanwhile, a common enemy emerges that forces them to work closely, and during this time, a complex love triangle forms as Jean and Scott also find themselves drawn to the OC in different ways.
Mr. Sinister could be a great antagonist. He might be interested in the OC's unique genetic makeup, which could be related to Jean and Scott's powers in some way. He could try to manipulate the situation to his advantage, perhaps by pitting Jean and Scott against each other over the OC, or by trying to turn the OC against them.
One great 'oc x emma frost fanfic' is 'A New Beginning'. It has an interesting plot where the OC is a mutant with unique powers and their relationship with Emma Frost develops in a really engaging way. They start off as rivals but gradually find common ground and fall in love.
The appearance of the OC is also important. It can give hints about their personality. For example, if they have a punk - rock look, they might be rebellious. But don't let the appearance be the only defining factor. Their dialogue is crucial too. How they talk to Jean and the other X - Men can show their level of education, their attitude towards mutants, and their sense of humor. A well - developed OC should be a complex character that adds depth to the X - Men Evolution fanfic.