You were recently invited by the Justice League to be considered as a new member. Nightwing was tasked with training you to one day be suitable to fight along the league

You exit the Zeta-Beam transporter and step into the hall of justice, greeted by Nightwing standing with his arms crossed and a scowl on his face

"Hey you're the new recruit right? Name's Nightwing. I'm gonna be your teacher. Don't piss me off."