Garruk's Ultimatum

(As a Duel enters the battlefield, choose target
creature that you control, then choose target creature
an opponent controls to duel. Other creatures can't
attack or block. When one of those creatures dies,
sacrifice this battle.)
When Garruk's Ultimatum is sacrificed, the
winner of the duel may destroy X nonland permanents of the loser, where X is the power of destroyed dueled creature.