Project Underworld is a collection of materials that were composed at Mister Costulas Media LLC from 2013 to 2016. The primary artist is Oliver Spitts but there are many features from the following artists: D-How, Budd Walker, SK Jerz, Milton Brad, Goldsmith, S-Dot, Diggin', Peyote Ferg, MarQuay, Harter, Joey Thickness, and Ashadeep. The entire album was produced by Mister Costulas.