With four games in the Batman: Arkham series spanning from Arkham Asylum to Batman: Arkham Knight, fans were given seemingly all the content needed to have the ultimate Batman experience. As it turns out, though, the developers were even more ambitious than fans realized.
Many ideas were presented to each Batman: Arkham game, from the inclusion of certain villains to certain content that was never finished. Some were able to be reused in subsequent titles, but some proposed Arkham content sadly never saw the light of day, despite how appealing these features may sound to the series' devoted fans.
More Weather Effects (Arkham Origins)
The wintery Gotham City of Arkham Origins is one of many reasons why the prequel is considered to be underrated. Apparently, there was supposed to be even more to the weather that is present throughout the game such as whiteouts.
Whiteouts would cause the city to become a void of white which would have forced players to use Detective Vision is navigate. It's not much but it would have added a nice bit of challenge to traversal. However, it was removed from the game due to worries that it would annoy players.
Black Mask (Arkham Knight)
Though he ended up being a rather short final boss for the Red Hood DLC, Black Mask was originally intended to be one of Gotham's Most Wanted missions in Arkham Knight.
Game files were found that indicated that Black Mask was going to be a DLC mission for the open-world map. Instead, Black Mask was simply repurposed in one of the weakest bits of DLC in the Arkham series. This isn't the first time Black Mask was poorly used as he ended up being the Joker in disguise in Arkham Origins.
Joker AR Challenge (Arkham Knight)
While the Batmobile was a tad overused in Arkham Knight, one augmented reality challenge would have made players overlook that. It would have had the Joker piloting the Batmobile with the objective being to cause as much destruction as possible.
The more property damage, the more points are given to the player. It was going to be called Million Dollar Mayhem but sadly, it never made it to the game.
Mad Hatter's Hedge Maze (Arkham Asylum)
Most of the original Arkham Asylum's lost content would end up being retooled for other games. However, one bit of content was never seen again and that was the hedge maze. It would have had Batman being guided through the maze until in the center was Mad Hatter hosting a tea party.
Unfortunately, the only thing remaining of this content is the Hatter's tea set being the answer to one of many riddles sprinkled throughout Arkham Asylum.
More Playable Villains (Arkham Origins)
In Arkham Asylum and Arkham Origins, fans were able to play as villains via challenge mode. However, according to one of the developers of Arkham Origins, there was supposed to be more. Sections of the main story and even open-world segments were supposed to have villains as playable characters.
This could have led to more to do in the Arkham Origins map which, while visually pleasing, left a lot to be desired when it came to content. Especially since Arkham games feature so many memorable side missions.
Prometheus (Arkham Knight)
Despite being teased through multiple Easter Eggs across the games, Prometheus never made a physical appearance. Not even as a simple cameo. Well, that was originally supposed to change as proven by the same files in which Black Mask was found, there were also files on Prometheus being a DLC villain.
Unlike Black Mask who was able to be repurposed, Prometheus was scrapped altogether. This was a shame since Prometheus likely could have made for a stand-out boss fight of the Arkham franchise.
Worst Nightmare Skin (Arkham Origins)
Throughout Arkham Origins, things are shown from the Joker's point of view. He views Batman as a demonic shadowy bat-like creature. This design was almost a playable skin in Arkham Origins and was even shown off at the San Diego Comic-Con of 2013.
Sadly, it was removed from the game since it apparently was the cause of many errors within the game. A similar idea was used in Arkham Knight with the mysterious and fiery Batman figure seen at the end but it was only used for that cinematic.
Victor Zsasz's Return (Arkham Knight)
Within the chaos of Arkham Knight, Victor Zsasz can be found as the smallest of cameos via surveillance footage. In a twist, it would seem that Victor was going to play a larger role within the game due to audio files being leaked featuring Victor Zsasz doing his usual serial killer schtick.
There is also audio of Batman putting Zsasz into a cell. Perhaps since Zsasz and Professor Pyg are very similar and equally disturbing Batman villains, Rocksteady likely scrapped Zsasz to seem less redundant. All of the audio can be found on YouTube by the same person that found the files.
Even More Skins (Arkham Knight)
Batman has an abundance of skins in Arkham Knight, some of which make for some of the best skins of the Arkham series. Whereas Robin, Catwoman, Nightwing, Batgirl, and Red Hood all lacked when it came to their alternate skins, Batgirl never even got an alternate.
It turns out that there were plans for more skins as shown through an official poster banner teasing more skins before Rocksteady stopped working on Arkham Knight altogether. Some of these skins included a Grant Morrison Red Hood, another armored Batman, and a Damian Wayne skin for Robin.
Canceled Damian Wayne Sequel
Most would agree that the Batman story ended things properly with Batman: Arkham Knight; forcing another sequel would just cheapen the finality of Arkham Knight's ending. This is more than likely why the fifth Arkham game was scrapped.
Before Rocksteady moved onto Suicide Squad: Kill The Justice League, they were originally developing a sequel in which Damian Wayne is the new Batman. It would have featured villains such as an older Two-Face and the daughter of Black Mask. There was even concept art for the game released that promised a cyberpunk version of Gotham City.