Bellatrix was one of the first characters I came up with when I decided to start writing stories to post to DeviantArt. She was the main character one of the original three stories I had planned, not counting the Nancy in the Box segments. I wanted to set her up as Lilly's rival and introduce her in A Slave to the Omnisuit, asll they are all parted of the shared Trivium universe. However, it took me longer than I thought to get to her and I have yet to start writing her story.
She first shows up in Chapter 16 of A Slave to the Omnisuit, and I plan on having her appear in later chapters. She has a much larger role in Fox Hunt and I plan to give her a more involved role in an upcoming story before moving onto the one centering around her.
In case you were wondering, the other two of my original three story ideas were A Slave to the Omnisuit and All that Glitters, with Bellatrix's story still being unnamed.