Korra could meet the founders of the different bending disciplines. She could meet the first water benders and learn about the purest form of water bending. This would not only enhance her own skills but also give her a deeper connection to her water - bending heritage.
If we follow the more traditional route, Mako could be the father. They had a relationship in the show, and it would be a natural progression for them to start a family. Their relationship had its ups and downs, and the pregnancy could be a new chapter in their story together.
Well, one possible plot could be that Korra and Asami decide to start a family together in a modern AU. They face challenges like how to balance their important work with raising a child. Maybe Korra has to deal with her bending powers during pregnancy, like how to control them without endangering the baby.
Well, you might find fanfictions where Azula's character undergoes a transformation and acquires healing bending through unexpected circumstances or as part of a character growth arc.
Well, one interesting plot could be Clary slowly regaining her memories through a series of magical encounters. Maybe she finds an old object that triggers flashes of her past. Another could be that her friends play a crucial role in helping her get her memories back, like they take her to special places related to her past. And a third possibility is that there's some sort of enemy who is trying to stop her from getting her memories back, which adds a lot of suspense to the story.
One possible plot could be Korra going back in time to prevent a great disaster that she has knowledge of in her own time. For example, she might go back to stop the start of a war that had long - lasting negative impacts on the world. She could use her bending skills in new and unexpected ways in the past, as the technology and bending styles of that time might be different.
Clary is the central figure. Valentine might also be involved in some fanfictions, either as an obstacle trying to prevent Clary from getting her memories back because he doesn't want her to discover certain secrets, or in a more complex way where his past actions are somehow related to the loss of her memories in the first place. And of course, the Lightwood family members are likely to be involved, given their importance in Clary's life and the Shadowhunter community.
The 'lemon' aspect might be a bit hard to come by in a clean way as it often involves inappropriate content. But for normal Korra and Mako fanfictions, you could also try FanFiction.net. Some stories there might show their relationship developing, their adventures together, and how they support each other, which can be really interesting to read.
Well, a mind-bending story often involves challenging conventional logic. You could introduce time loops or alternate realities. Also, make the reader constantly second-guess the narrator's reliability. And have a climax that completely upends all expectations.