Yesterday Square Enix announced the NieR: Automata DLC titled 3C3C1D119440927. More information and gameplay for the DLC was shown today during a livestream.
The DLC will be a battle arena hidden by one of the apologetic machines that previously stood in front of inaccessible doors. Completing rounds in the underground battle arena will unlock various prizes such as masks with special effects and cosmetic items. These new cosmetic items include a Kaine outfit for 2B, a young Nier outfit for 9S, and old Nier outfit for A2. There will also be various hair dyes available. Video of this was shown today and can be seen below courtesy of DualShockers.
This may be a bit of a spoiler for some, but
Nier: Automata DLC 3C3C1D119440927 is currently set to launch in Japan May 2nd. No release date has been given for other regions.