Enter The Gungeon (universe)

Enter the Gungeon is a bullet hell roguelike video game developed by Dodge Roll and published by Devolver Digital. The game was released worldwide for Microsoft Windows, OS X, Linux, and PlayStation 4 on April 5, 2016, on Xbox One on April 5, 2017, as well as on Nintendo Switch on December 14, 2017.

Its main relevance in the server is zeros character he uses "gunhead" orginates from the game