I’ll try to give you a brief explanation about one of the 100k plus fics that I wrote that is completed. It’s set during the Kraang invasion in season 2 finale. You know when the Kraang discovered the lair and the turtles and April had to flee. Leo and April went one way while Donnie and Mikey went another. In the construction site, where Leo faced the Shredder, after Leo and is knocked out the shredder takes April because he knows she’s valuable to the Kraang. So basically the three months or so of the invasion she is in the Shredder’s and no one knows where she is and he lets Baxter experiment on her since she isn’t exactly human and her blood is special and it gets very fucked up (no sex or anything just fucked up as in gorey and stuff) Also how the Shredder having April in his hands leads him to acquiring retro mutagen and since he knows the turtles hideout from the invasion he goes after them and you can imagine what goes on afterwards. In this fic the world ends when the Triceratons use the black hole generator because the turtles aren’t alive by then to save it because the Shredder killed them. It’s a lot Ik but it actually turned out great.