{0}: Mist Dragon gains flying. (This effect lasts indefinitely.) {0}: Mist Dragon loses flying. (This effect lasts indefinitely.) {3}{U}{U}: Mist Dragon phases out. (While it's phased out, it's treated as though it doesn't exist. It phases in before you untap during your next untap step.)
"Across the plains, farmers who braved the mists began to vanish. Most blamed the goblins; none guessed the truth." —Hakim, Loreweaver