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A Decompressor is a piece of machinery found in the Ruby Passage level, The Curious Factory in Wario Land 4. It is a machine that reverses the effects of a Compressor, which crushes Wario and turns him into Flat Wario. The Decompressor decompresses Flat Wario's body, turning him back to his normal self.
The Decompressor is a silver-grey color and appears to be made out of metal. It is cube shaped with two openings, one at the front and one at the back, for Wario to pass through. Two floor-level windows are on the front so that the player can see Wario getting recompressed. Yellow lights flash above the two openings and the windows. Wario in his normal form and even enemies can pass through a Decompressor without any effect. Besides the Decompressor, Flat Wario can also change back into his normal form by touching water.