[user104658]

I don't know if this is part of a series? I get the impression it's a standalone project and not related to the Arkham universe. Although Batman did "die" at the end of Arkham Knight, if I remember rightly... but it was made clear that he wasn't actually dead, just took on a sort of "myth" status but was actually still around, just less visible.

I dunno I finished Arkham Knight years ago .

Nightwing does look a lot like the Nightwing from that game, but they might just be based off of the same reference material.