Nasty Evil Fog

From Zelda Wiki.org

This purplish fog is found only in the Earth Temple. If Link enters this, he will become "cursed", meaning that none of his items work, including his sword. The curse will not be lifted unless you get out of the fog or find a Light Beam. The Deku Leaf can blow the fog away from a small area at a time. The effect is similar to being cursed by a Blue Bubble.