is a fan-made, "custom" modification of the original Windows 8 operating system. These "Underground" or "Black" editions were popular in the early 2010s on file-sharing sites like The Pirate Bay and various tech forums, typically created by enthusiasts to strip away bloatware and add custom visual themes. The Concept
It often featured "Dark Mode" themes long before Microsoft officially supported them, along with custom icon packs and wallpapers that gave it a sleek, aggressive look. Windows 8 Underground Edition 2013