The Scarecrow Nightmare Pack detailed
Scarecrow's reveal during the Sony E3 2014 press conference was a highlight. Woke me right up, it did. Batman: Arkham Knight was yet another one of those games to (annoyingly) have system-exclusive content -- in this specific case, the Scarecrow Nightmare Pack on PS4.
Fear toxin has turned Gotham into a "twisted, hellish nightmare," reveals a product listing on PlayStation.com. "Tear through the city in the all-new Batmobile and face off against a towering vision of Scarecrow and his undead army as they spread terror on the streets, available exclusively on PlayStation 4."
Some folks played Arkham City but skipped the game that started it all, Arkham Asylum. They missed out. The original is still worth playing for the trippy Scarecrow sections.