The latest trailer for Batman: Arkham Knight has emerged online, ahead of the game's release date on June 23, revealing a new gameplay feature.

As well as showcasing some of Gotham's most notorious villains, such as Two-Face and Scarecrow, the video also reveals two Batman sidekicks for the first time. Both Nightwing, Robin, and Catwoman can be seen fighting alongside the Dark Knight, at times performing tag-team manoeuvres.

Publisher Warner Bros. has revealed that Batman: Arkham Knight’s will feature a new gameplay mode, called Dual Play, which lets players "seamlessly switch between The Dark Knight and his allies including Robin, Nightwing, and Catwoman in freeflow combat." This sounds similar to how Rockstar's Grand Theft Auto V allows players to freely switch between the game's three main characters.

Azrael is also shown in the new trailer.

Arkham Knight will be the first title in the series given an M rating in North America--roughly the equivalent of an 18 certificate in the UK--which suggests a darker tone for Batman's showdown with his time-worn foes.

In a recent interview, Rocksteady founder and Arkham Knight game director Sefton Hillspoke of the challenges in creating some of the darker content. He said that publisher Warner Bros did a ratings analysis on the game and concluded that certain scenes would be likely to cause "issues." Hill received an email informing him that these scenes--which remain a mystery--might need to be cut.

Losing these scenes, which are reportedly central to the game, could have "destroyed" the project, Hill said. However, the developer later spoke with a DC Comics executive who agreed to allow the scenes to stay, though it's unclear if they were altered in any way.

"We're not including gratuitous blood or swearing," Hill added.

"We want to deliver a true end with no compromises, and it takes us to some dark places."

Originally intended to be released in 2014, Batman Arkham Knight's release date has been delayed again, this time to June 23. The game is coming to Xbox One, PlayStation 4, and PC.