Okay so the Ing will be the bad guys, no i just need to put this story somewhere along the shows timeline.

should it be during the season 3 finalie or after it

or should it during the season 2 finalie or after it?

help me decide

That depends on what you're looking for in the setting. Do you want alicorn Twi to be in your story? If so, post season 3 finale. No? Before that. Just think about things like that and you should be able to figure it out for yourself.

That said, I personally would set it after the season 3 intro special- perhaps Sombra had something to do with bringing the Ing to Equestria.

944023 not a bad idea, i'll think about it

Post season 3. Powerful Alicorn Twilight is wonderful!!! I like the idea of pumping her full of magic, then setting her naive self on Equestria and seeing the chaos that occurs.

Hmmmm, IDEEAAAA!!!! Dark Discord!! Discord possessed by Ing!!! MAKE IT HAPPEN!!!

The ing exist in a parallel universe to the Metroid universe, so it'll be interesting to see how you work that out. Also, no cliche character gets possessed and becomes bad guy fics please. Those are like, the only Ing fics you ever see, and they're kind if bad. Create a backstory for the Ing. Nothing exists for no reason, so giv me then a reason. Also, post season three means twilight can be a badass battlemage, and that's always good.