Nightwing
Although Nightwing is commonly associated with Batman, the title and concept have origins in classic Superman stories. The original Nightwing in DC Comics was an identity assumed by alien superhero Superman when stranded on the Kryptonian city of Kandor with his pal Jimmy Olsen. Drawing inspiration from Batman and Robin, the two protect Kandor as the superheroes Nightwing and Flamebird. Following the Crisis on Infinite Earths continuity reboot in 1985, Nightwing was re-imagined as a legendary vigilante from Krypton whose story inspires Dick Grayson's choice of name when he leaves behind his Robin identity.
Nightwing
Batman then entrusts Nightwing to alert other heroes about the danger that the Crisis poses. Dick flies to Titans Tower, but due to the chaos resulting from the Blüdhaven disaster, the OMAC onslaught and other Crisis related events, the only hero who answers his call is Conner Kent. Together, they locate and attack Alexander Luthor's tower, the center of the Crisis, only to be repelled by Superboy-Prime. Prime is ready to kill Nightwing when Conner intervenes, sacrificing himself to destroy the tower, ending the destruction of the Universe.