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The Dummy Plug Plant, or Deep Underground Facility: Central Area, is a room deep within the bowels of Central Dogma that is used to house the soullessRei vessels that are said to be the cores of the Dummy System.
The arrangement of the "brain", the "spinal column", and the tank of LCL in this room is possibly supposed to resemble a primitive version of the Evangelions' entry plug system. The brain-like object in the metallic casing is possibly a product of the same technology as the "brain" in the Magi system.
During Episode 23Ritsuko destroys the soulless Rei clones by initiating "Destrudo Release", which causes them to disintegrate.