Morphling, Elemental Comet

Morphling comes into play with
Power and Toughness {x}
Once per turn, you may shift any number of Morphling's Power
into its toughness or vice versa
{4}{g}{u}, Morphling becomes a copy of target
creature or planeswalker in play
for the rest of the turn, except it is not legendary
if the permanent is legendary.