Mist Dragon is a rare Creature — Dragon card from Mirage (MIR), collector number 79. Current market price: $3.50, TCGplayer market prices via Scryfall.
{0}: This creature gains flying. (This effect lasts indefinitely.) {0}: This creature loses flying. (This effect lasts indefinitely.) {3}{U}{U}: This creature 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.)