For the bounty progress, you will need 500 points. Every time you get a kill with a void weapon/ability you will recieve 5 points toward the bounty. However, everytime you die, you will lose 2 points. I think out of all of the crucible exotic bounties, this is one of the most difficult. You will basically have to get kills with any weapon/power that uses void. Look in your inventory to see if you have Shotguns, Fusion Rifles or Sniper rifles that do void damage. You will want to use those to progress your bounty. Also, if you are a Titan, you will probably want to use the defender subclass, since that uses void. The super will help you stay alive, and the grenades might net you a kill here and there. I did it with the voidwalker subclass for the warlock, and a void fusion rifle. I picked a fusion rifle with a very small charge time and went to town racking up kills. As for you, if you are a titan, especially if you choose to play as a defender, you will probably want to look for a shotgun that does void damage, as that is the easiest way for you to rack up void damage kills.