^{From source:}

Aura Sparkle: How did you lose your wing, daddy?

Flash Sentry: I lost it protracting you and mommy. 

Aura Sparkle: oh… Do you ever regret losing it? 

Flash Sentry: Not for one second.    

Flash lost his wing in a fight with a Manticore terrorizing Ponyville. Fluttershy was out of town. So Flash spend up to get rid of it. And all most died in the process. At the time Twilight was pregnant with Aura Sparkle. So she was scared the hell he was going to die. Thankfully he lived. Flash realizing he could have died with Twilight in tears and never seeing his baby. So Flash retired from the royal guard. How ever Flash still help teach the up and coming royal guards.

Aura Sparkle is a part of my MLP: next gen. She is the daughter of Flash Sentry and Twilight Sparkle.

Fun fact: Mommy Twilight has the same body type and high as Luna. So Twilight is actually taller the Flash.

Background made by The vector for Flash’s CM was found of the  EG wiki.