When a creature becomes warded, place a ward status counter on it. If a creature with a ward counter on it would be damaged, destroyed, or leave play, instead discard each ward counter on it. (Note: This prevents the creature from being tagged for destruction.)
While a creature has a ward counter on it, it cannot be warded again.
If a ward counter is placed on a creature after it has already been tagged for destruction, the ward counter will not prevent the creature from leaving play. However, it will prevent the creature from leaving play in other ways, such as being returned to hand.
Once a creature has been tagged for destruction, it's too late for the creature to be saved by a Ward. While a Ward can prevent a creature from being tagged for destruction, it will not prevent an already-tagged creature from leaving play.Source: Crucible Cast 17