meddler
Pony Flash Sentry is actually several hundred years old. He was alive when Equestria was first founded, and traveled to the Crystal Empire to fight against Sombra as a Robin Hood-esque figure. His luck ran out when he was captured and flung into the future with the rest of the Empire.
After Sombra’s final defeat, Flash left the Empire to try and reconnect with the rest of the world, but felt alienated by how much everything had changed. He returned to the Empire and joined the Royal Guard, having found purpose there and plenty of old friends who were going through the same problems.
Also, Flash Sentry is Twilight’s great-great-great-great-great-great-etc-uncle. Neither of them know about this.
After Sombra’s final defeat, Flash left the Empire to try and reconnect with the rest of the world, but felt alienated by how much everything had changed. He returned to the Empire and joined the Royal Guard, having found purpose there and plenty of old friends who were going through the same problems.
Also, Flash Sentry is Twilight’s great-great-great-great-great-great-etc-uncle. Neither of them know about this.