The standard stage of this challenge must be completed to unlock Harley Quinn/Arkham Knight. Like all challenges, it has three stages of difficulty - Standard, Expert, and Nightmare. Each stage has 63 matches, divided into 5 challenge battles. There is no particular order for the battles, but the whole stage must be complete before it will be reset to a higher difficulty level.
- The "title" as well as the description of the challenge refers to its character as "Arkham Knight Harley Quinn", despite that her special 1 card refers to her as "Harley Quinn Arkham Knight ", as it normally is for official naming conventions.
- Prior to the challenge, the Arkham Knight Harley Quinn Pack is released and allowed players to obtain her along with her gear and support cards with real money, also the Arkham Pack can be bought with credits and was already available before due to a glitch.