If you own the base game but cannot find a DLC key, some community archives exist. This is if you legally own the DLC on another platform (e.g., PlayStation) or purchased a key that Steam no longer recognizes.
However, time has been kind to the game. It features what many consider the best boss fights in the entire quadrilogy. Battles against Deathstroke, Firefly, and Bane are kinetic, cinematic encounters that test your mastery of the Freeflow combat system. The narrative, which explores Batman’s first encounter with the Joker, is a tragic and gripping story that rivals the writing of Rocksteady’s entries. Furthermore, the "Cold, Cold Heart" DLC remains one of the best story expansions in the franchise. Batman Arkham Origins Pc All Dlc Download