Haze is a poisonous, purple gas that is impenetrable without the aid from an Etherillium Tube to clear it away. There are numerous diseases associated with inhalation of haze. It is said that exposure to haze would easily knock out a person within 2.5 minutes. Prolonged exposure is lethal.
"When the Skystone exploded, waves of Haze enveloped the land. Haze is given off by invasive fungi that have quickly covered the land. Haze is poisonous to all native creatures, including humans. However, Mimics thrive in the Haze." --Sprocket "Skystone 101: Haze"
"Haze Pillars are produced by massive fungi that encase the fragments of the Skystone. These pillars are major sources of the spreading Haze. The Nidarian army uses these pillars as key points for the land reclamation effort." --Sprocket "Haze: Pillars"
"Three years after the Skystone explosion, the Haze engulfed 25% of the land. This caused a massive exodus known as the Great Displacement. Haze-free areas soon became overpopulated by vast amount of refuges." --Sprocket "Haze: The Great Displacement"