The Tarsus Scorpii

Once per Fight phase, after rolling a hit roll of 6+ for this weapon, CARAB CULLN THE RISEN may choose to grab his foe in a death-hold. You may choose to fire his heavy bolter at point blank range - inflicting D6 mortal wounds on the target in addition to the normal damage. This ability can only be used once per game - if the death-hold ability is used, then the heavy bolter may not be fired for the remainder of the game.