As long as an opponent controls a creature with flying (This creature can't be blocked except by creatures with flying or reach.) not named Escaped Shapeshifter, Escaped Shapeshifter has flying (This creature can't be blocked except by creatures with flying or reach.). The same is true for first strike (This creature deals combat damage before creatures without first strike.), trample (This creature can deal excess combat damage to the player or planeswalker it's attacking.), and protection from any color (A permanent or player with protection can't be targeted, enchanted, equipped, fortified, damaged or blocked by sources of the given property.).
Vintage
Modern
