Shulesh, Dead of Winter

Flying, Ward—Tap a permanent you control.
At the beginning of each opponent's end step,
that player chooses X tapped permanents they
control, where X is equal to the number of snow
permanents you control. Those permanents
don't untap during that player's next untap step.
Whenever a spell or ability you control targets a
permanent an opponent controls, you may tap
that permanent.