Nagash, Soul stealer

Soul Stealer is a spell that has a casting value of 6 and a range of 24". If successfully cast, pick 1 enemy unit within range and visible to the caster and roll 2D6. If the roll is greater than that unit its Bravery characteristic, it suffers D3 mortal wounds. If the roll is at least double that unit its Bravery characteristic, it suffers D6 mortal wounds instead. You can heal up to 1 wound that has been allocated to the caster for each mortal wound caused by this spell that is not negated.