Curse of Exsanguination

If successfully cast, pick 1 enemy unit within range and visible to the caster. That unit suffers 1 mortal wound. If that mortal wound is allocated to a model in that unit and that model is not slain by that mortal wound, roll a dice. On a 3+, that model suffers 1 mortal wound, and you can roll another dice if that mortal wound is allocated and the model is not slain. Keep rolling dice in this way until no mortal wound is caused, the mortal wound is negated or the model is slain.