When Superboy goes back to Cadmus to find out more about his creation (Along with a few other YJ members) they find out that Cadmus did not end with Level 52. There was a Level 53. (I will not spoil what happens so that is the best description I can offer you. Please enjoy my 2nd fan fiction!)

Everything ended that fateful day... His parents died... Nobody listened when he told the truth.. No one saved him from the man... No one heard his screams and cries.. Now he's gone.. On that day.. Richard Grayson died and Renegade was born.. Instead of being adopted by Bruce Wayne, Richard Grayson went wiling with Deathstroke aka Slade Wilson. Becoming his apprentice. What happens when he encounters the Young Justice League during one of his missions alone and saves one of the heroes? xxxxxxxxx An AU based off of Richard Grayson the very first Robin ALSO ON Archive Of Our Own.org by the user PrinceLilah

Bruce Wayne never went to the circus on the day the Graysons died, meaning he never adopted their orphaned son, Richard. Dick went to a Juvenile Detention Centre for eight months before spending a year going in and out different foster homes, each one rejecting him, now he's in a Gotham orphanage. Five years after the Graysons death, and there's a new black haired, blue eyed thief in Gotham, nobody knows who he is, it's a mystery. So that's what they've called him- Mystery. Mystery constantly annoys the Justice League and their sidekicks, occasionally helping out when it suits him. The Justice League know nothing about the young boy and its starting to frustrate them, especially Batman. What happens when they find out that Mystery is just Richard Grayson, a messed up orphan? Will they decide to send him back to Juvie or help him? Unknown to the Justice League, he's running from something, but what? AU Disclaimer- I don't own Young Justice