Before Lance-Corporal Susan "Seraph" Shelby was recruited to XCOM, she was a UN peacekeeper in the disintegrating Nigeria. Before that, she was a promising officer candidate in the US Army. Before that, she attended the school that could have kept XCOM's researchers busy for years, had they existed.

Before that, her name was Sunset Shimmer.

Now, with her past and future catching up to her, LCPL Shelby must wrangle her mistrustful fellow soldiers, an alien invasion with a renewed purpose, and a very different world beyond the mirror.

(Takes place during XCOM: Enemy Unknown/Within. XCOM 2 is not canon to this story.)