The upcoming Mayhem Collection DLC for LEGO Batman: Legacy of the Dark Knight Deluxe Edition will introduce a new story mission starring The Joker and Harley Quinn, alongside an all-new Mayhem Mode and the Sinister Pack. The downloadable content will be available for free to all Deluxe Edition owners on September 18, 2026, coinciding with the game's launch on the Nintendo Switch 2.
The central addition of the DLC is a story mission where The Joker and Harley Quinn collaborate on an Arkham Asylum breakout. Players can expect Harley Quinn to utilize her signature hammer and Fun Gun, and also summon her hyenas, Bud & Lou. The Joker will employ his Paintball Pelter and Boxing Glove, with a combat style emphasizing speed and mobility. The DLC will also allow players to unlock outfits for both characters inspired by various Batman media, including The Dark Knight Returns comic series and Batman: The Animated Series.
Beyond the story content, Mayhem Mode will see Harley Quinn and The Joker unleashed across Gotham City for time-limited "Mayhem Runs." During these runs, players must race back to Amusement Mile before time expires, all while evading Batman and Robin. Earning LEGO studs will involve destroying the environment and completing challenges, while also battling DC villains such as Deathstroke, Killer Croc, and King Shark.
The Sinister Pack adds themed outfits derived from prominent DC comic book issues and action figures. This pack also includes a new vehicle, the Jokermobile from the Arkham Trilogy, and Batcave customization options. Notable outfits include The Batman Who Laughs for Batman and Joker-themed outfits for characters like Robin, Nightwing, Batgirl, Jim Gordon, and Catwoman, many referencing specific comic issues or the Jokerized DC Multiverse action figure.
Additionally, an enhanced 'Absolute' difficulty level will be released as a free update for all players on the same day. This new mode is described as requiring "greater skill, awareness, and precision in combat."
LEGO Batman: Legacy of the Dark Knight originally launched in May 2026 for PlayStation 5, Xbox Series X/S, and PC. Reviews at the time praised its "strong open-world Gotham and trademark Lego slapstick humour."