At one point in Batman: Arkham Origins, you get a side quest to find all of Penguin's weapon caches that are hidden through the city. For every cache you find after the first, a message similar to this one is displayed:
Where is Penguin's Black Market? I don't see any waypoints on my map, and the case file for the Penguin is listed as Completed. I went through his base again, but it is completely deserted.
Best Answer
Penguin's Black Market is a multiplayer-only feature. It allows you to purchase crates containing gear and other items for use online.
When you enter the store, you will be greeted with notifications that you have some crates and are given the option to open them. I don't think the items you get from the crates are predetermined, it appears to be random.