Omen of the Scarecrow

Scarecrows you control gain the following effects:
•{ut}: add {c}. this mana can only be used to cast
Scarecrow spells or activate the abilities of
scarecrows. can only activate this ability once a
turn and at any time you could cast a sorcery.
•{g/w}{g/w}{ut}: destroy target non-scarecrow artifact
your opponents control.