Moonmist | Magic: The Gathering
Formats Moonmist is Legal in
Official Oracle Text for Moonmist
Official Rulings for Moonmist
9/22/2011 : Whether or not a creature is a Werewolf or a Wolf is checked only as combat damage is dealt. If the creature isn't a Werewolf or a Wolf at that time, its combat damage will be prevented.
9/22/2011 : Moonmist will prevent combat damage dealt by a creature that isn't a Werewolf or a Wolf even if that creature wasn't on the battlefield (or was a Werewolf or a Wolf) when Moonmist resolved.