Invasion is a DLC map from Map Pack 2.
Invasion is a map with a preset maze similar to Complex but allows the players to build Amp Fields, Killing Floors, and Slow fields. It appears to be inside a factory with conveyor belts and other devices on the ceiling. The waves spawn out of two large growths east of the maze where they travel west and circle back around to the core. Towers can be built behind the spawn point and all around the maze on small raised segments. Each level is 15 waves long and forces the player to fight off 2 lines of enemies.