Extermination Day (formerly known as Hell on Earth Starter Pack) is a 35-level WIP megawad add-on for Brutal Doom, created by Marcos Abenante (Sergeant Mark IV) and initially released on December 31, 2015. It is intended to be loaded with Doom II or Freedoom, using the included version of GZDoom which is pre-configured for play. The most recent version is a work in progress and is in a nearly finished state as of May 2020. The megawad remakes Doom 1 and Doom 2 level design in a Build engine style. The first two levels from Duke Nukem 3D are also remade as secret levels. Several maps that Abenante created earlier have been remade to flow with the megawad.