The page below contains MASSIVE SPOILERS of the main Breath series, read with precaution.
Twilight Sparkle is a minor character in the main Breath series and a major character in Breath: Crimson Darkness and Breath: The Fall of Celestia. She's notable for being an actual character from the My Little Pony: Friendship is Magic show.
Breath: Crimson Darkness and Fall of CelestiaEdit
"Haha, no silly, you're alive!" - Twilight to Skyblack in Crimson Darkness 14.
Twilight is Crimson's girlfriend in the series. She is the one that makes the plans and tell them what to do to take down Celestia.
"Don't take me wrong but, erm...get a job, you know? You need bits if you don't want to end up as a homeless junkie!" - Twilight to Skyblack in episode five.
Twilight makes a brief appearance in episode four, helping investigators with the case of the murdered pony in front of Skyblack's apartment, and appears again in the next one, meeting Skyblack and Fluttershy.