Anivia, the Cryophoenix

Flying, vigilance
At the beggining of your upkeep, if you control
six or more lands, return Anivia from your
graveyard to the battlefield. Untap all lands
and creatures.
Ultimate — {g}{w}{u}, {t}, sacrifice Anivia:
Tap all creatures and lands. They don't untap
during their controller's next untap step.