The Dark Goddess

Nyx isn't a Hargreeves, but she grew up in the shadows of their mansion all the same. Left to her ordinary parents in an ordinary world, she and Five used to play as young children.

In a mistake of power and control, Nyx fell through her shadows and became trapped in a different reality, one where the world was destroyed and a Commission controlled all matters pertaining to time and space.

Five defies his father in an attempt to find Nyx and accidentally becomes trapped in a post-apocalyptic future.

(For story reasons, Nyx and Five rejoin in their 20s and he does not meet Delores.)