Morkai's Teeth Bolts

“When you give a model this Relic, select one bolt weapon (pg 38) that model is armed with. When that model is chosen to shoot with, you can choose for that weapon to fire a Morkai’s Teeth bolt. If you do, you can only make one attack with that weapon, but if a hit is scored, the target unit suffers 1 mortal wound and that unit is marked by Morkai until the end of the turn. When resolving an attack against a unit that is marked by Morkai, re-roll a wound roll of 1.