Thunderbolt Heavy Fighter

Some models have 'Deadly Demise x' listed in their abilities. When such a model is destroyed, roll one D6 before removing it from play (if such a model is a TRANSPORT, roll before any embarked models disembark). On a 6, each unit within 6" of that model suffers a number of mortal wounds denoted by 'x' (if this is a random number, roll separately for each unit within 6").