The Invasion

The Invasion is a 2002 partial conversion for The Ultimate Doom which replaces all four episodes. It was created by Paul Fleschute (Moe) and it includes a wide variety of changes, including new enemies through DeHackEd, many new textures and sprites, new music, and a new storyline which pits the player against the Aldorian alien race as they attack several Starbases owned by the USEC. Through its many custom graphics and enemies, the WAD manages to create a peculiar atmosphere that still remains unique to this day.

Levels
The Rock: Project: Jupiter: Planet Hell: The Final Frontier:
 * E1M1: Launch Command
 * E1M2: Storage Area
 * E1M3: The Infirmary (Exit to secret level)
 * E1M4: Astoroid Mining Project
 * E1M5: The Caves
 * E1M6: Shipping Area
 * E1M7: The Observatory
 * E1M8: Command Station
 * E1M9: Central Processing (secret level)
 * E2M1: Security
 * E2M2: Containment Area
 * E2M3: Refinery
 * E2M4: Central Processing
 * E2M5: Central Command (Exit to secret level)
 * E2M6: Sickbay
 * E2M7: Power Control
 * E2M8: Terror
 * E2M9: Nuclear Plant (secret level)
 * E3M1: The Brigs
 * E3M2: City of Takira
 * E3M3: Temple of Doom
 * E3M4: Threshold of Hell
 * E3M5: Chaos
 * E3M6: Deep Beneath (Exit to secret level)
 * E3M7: Mt. Eldanar
 * E3M8: Death Domain
 * E3M9: Forbidden Temple (secret level)
 * E4M1: Fear
 * E4M2: The Jefferies Tubes (Exit to secret level)
 * E4M3: Perfect Hatred
 * E4M4: Cargo Hold
 * E4M5: Engine Control
 * E4M6: Detention Level
 * E4M7: Circle of Death
 * E4M8: Mission: Impossible
 * E4M9: Halls of Hell (secret level)