LEGO Batman: Legacy of the Dark Knight’s Mayhem Collection DLC launches September 18 on Xbox Series X|S

What we know

LEGO Batman: Legacy of the Dark Knight’s Mayhem Collection DLC will launch on September 18, 2026, for Xbox Series X|S. The expansion shifts away from the base game’s hero-led campaign by making DC Super-Villains The Joker and Harley Quinn its playable leads.

Its new story mission presents the team’s take on Harley’s origin. It begins with Dr. Harleen Quinzel and her first meeting with The Joker, leading into her transformation into Harley Quinn. Players will also see more of Arkham Asylum’s interior, starting with a look at an ordinary day there before the pair break out and stage a large farewell party.

From Arkham to a hideout beneath Amusement Mile

After escaping, The Joker and Harley head to Amusement Mile, where they set up a secret base beneath the Funhouse. Players can expand and customize the hideout through multiple areas to decorate, along with new Joker- and Harley-themed customization props.

The expansion draws heavily on Batman: The Animated Series, the show where Harley Quinn first appeared. Its references include cutscenes displayed in a 4:3 aspect ratio as a nod to the original TV format, alongside nods to other Batman shows, films, games, and comic stories.

Gotham City will also feature a shop named “Sorkin’s Gems,” paying tribute to Arleen Sorkin, Harley Quinn’s original voice actor, who died in 2023.

Mayhem Mode brings timed repeatable runs

The DLC adds Mayhem Mode, a repeatable, time-limited activity set in a locked-down version of Gotham City’s North Island. Each run lets players rob shops, smash ATMs, spray graffiti, steal vehicles, battle A.R.G.U.S. agents and Task Force X, and collect studs.

Studs earned during runs can be spent at the hideout on permanent upgrades, customization items, and 30 new outfits for The Joker and Harley. Players can also rescue Arkham inmates while exploring Gotham, then have them trained by Henchmaster—a character first introduced in Batman: The Joker War Zone #1. Those recruits can be assigned to a customizable crew that can be summoned to fight alongside the two villains.

Combat is intended to feel distinct from the main campaign while retaining familiar foundations. The Joker and Harley have abilities associated with the original playable characters, but the expansion puts greater emphasis on their new ranged gadgets. Both can move freely while using them, enabling a faster run-and-gun approach built for controlling enemy groups and keeping up with Mayhem Mode’s pace.

Mayhem Collection will also feature villain-themed LEGO builds that permanently affect the city. Through its story, progression systems, customization, and repeatable challenges, the DLC expands the game through the perspective of two of Gotham’s most recognizable antagonists.