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You tap WO at opponents endstep. With a tapped WO you are allowed to untap your lands and the WO - making it tax your opponent in his untap phase.
Tappning it in your own upkeep (i.e with tangor...

You can tap Winter Orb with Aether Grid! Then you get to untap!

This SCREAMS for winter orb. Do you know how good it is with Aether Grid? And with black vise?
With a real mana base you could also run daze. Its also great with vise since they will be anxious to...

Check out Interdict. Doesnt counter triggers but neither does shadow. Maybe shadow is better as it counters tutors of all sorts.