Twilight

The twilight is an ominous shroud that is trying to devour the land of Hyrule in hopes of the King of Twilight, Zant to turn whatever light is left in the world into shadow, allowing his people to freely live outside of the Twilight Realm. Zant, takes away the light from the Light Spirits that maintain the light of Hyrule in different regions, and by taking these away twilight is able to take over the land in a somewhat "paint-filler" way. Anything that dwells within twilight appears to be, turned into a spirit (in the case of Humans, Gorons, Zoras, etc.), or transformed by it (in the case of enemies). Link, being the Hero that bears the Triforce of Courage, is one of the few that is able to stay in a solid form (albeit a wolf) and can try to restore light to the provinces.