Millennia Invasion is a single level PWAD created by Doomguy 2000. The story starts off with an invasion planned back in 2988 BC and happens in the year 2012 AD. The main objective is to supposedly find the self destruction switch or find an way to somehow shut down the spaceship. The enemies include: 5 different enemies from Doomguy's Warzone (Tourette's Demon, Gay Rapist, Ceeb, Warrior of Hell and Gallant Don), Terry Crews from Joey's Challenge Pack, Mini John Heads from UAC Military Nightmare, fake actors with the monster tag, and Lady Gaga known as her alias Mother Monster. Millennia Invasion comes with two different versions: The normal version with 50,000+ monsters and high resolution textures, and a lite version without high resolution textures and has 10,000+ monsters. The level itself pays tributes to one of the levels in Doomguy's Warzone Gold Edition, 30,000 Levels, Heaven, UAC Military Nightmare, and The Worst Level Ever Made.
As with most Doomguy 2000 WADs up to this point in time, it was poorly received due to a number of factors. The level is actually based off the Star Wars Death Star prison section. Other complaints include, the joke build time of 5,000 years, death traps in most of the rooms, or some of them with random props. Some of the enemies can kill the player even in God mode. It was however, praised for the Jukebox in one of the rooms as it contains 40 different midi tracks. Despite Millennia Invasion being another epic failure by Doomguy, plenty of its resources were used in Atomic Attack by Uncle Cracker.