The Amorphous Man

Ward {4}. Protection from green.
When The Amorphous Man enters the battlefield, each player puts a 4/4 space creature
token with "you can't play creature spells. {4}{t}: sacrifice this creature." onto the battlefield.
At the beginning of your upkeep, if no players
control a space token, exile The Amorphous Man
and return him to the battlefield transformed
under his owners control.