If you were trying to 100% the game and this final secret achievement was the only one missing, worry no more.
The Green Demon Face
This “green demon face” is the entrance to the black market, it can spawn on floors 1 through 5, Oubliette, and Abbey of the True Gun with an abysmal spawn rate (I’ve seen 2 in 100h), once you enter the face you get the secret achievement.
Modding
First things first you’ll need to do is mod the game, called “mod the gungeon”, this is necessary for we need to use the console, the mod allows for that. The link below with instructions on installing:
Once the mod is indeed installed, when you enter the game, instead of the name “enter the gungeon”, it’ll be “mod the gungeon”, the first step done.
Shortcuts
The second thing is having the shortcuts unlocked.
Although is possible to find the entrance on several floors, most images I saw of other people finding it was on floor 3, so I used that shortcut.
Here is the link to the wiki detailing how to unlock each shortcut.
The Farm Itself
Now that you’ve gotten all the pieces of the puzzle together let’s get that achievement.
Once you spawn on the floor of your choice open the console ( with the key ~ or \) and use the command “give gungeon_blueprint”, this item will allow you to see the whole floor layout alongside secret rooms. (I don’t think you need to have this item already unlocked for this to work).
This will take a while, if you don’t find the demon head on the center of a room, restart and repeat giving yourself the blueprint item. Until you see a floor like this:
Once you do, repeat twice the command “give 50_casing” and enter the face to be free of this frustrating achievement
That's everything we are sharing today for this guide. This guide was originally created and written by Narval (PT). In case we fail to update this guide, you can find the latest update by following this link.