Herald of Inevitable Doom is a 27th level cleric Encounter power that was introduced for the Warpriest's Death Domain in Heroes of Shadow.
Herald of Inevitable Doom
Cleric Attack 27
A nimbus of black energy surrounds your enemy, telling it that its demise is near.
Close burst 5
Target: One enemy in the burst
Effect: The target grants combat advantage until the end of your next turn. The next attack made against the target before the end of your next turn deals 4d8 extra damage on a hit or a miss, even if the attack normally deals no damage on a miss. This extra damage cannot benefit from bonuses to damage rolls.