Clinging Mists (Dark Ascension) - Warlock Assistant (for Magic: The Gathering)

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Prevent all combat damage that would be dealt this turn.
Fateful hour — If you have 5 or less life, tap all attacking creatures. Those creatures don't untap during their controller's next untap step.

Rulings:

1/22/2011 In most cases, attacking creatures will already be tapped. They still won’t untap during their controller’s next untap step.
1/22/2011 Clinging Mists doesn’t track the controller of the attacking creatures. If one of them changes controller before its previous controller’s next untap step, it won’t untap during its new controller’s next untap step.

(Rulings updated 3 years ago)