Jay Rock00777: On the first mission on the moon when you get to the big door we're the dead guardian is after the cut scene and the door opens up a bunch of thralls come running out blast away at them when there in a group once all the thralls are dead just try to kill the thralls once they are done go to orbit go back to that mission and resume at the part at the door again i did it in 20 min just repeating that check point 3 times I was able to get 10 on my first try.