After finally reaching rank 50 in dead orbit you are rewarded with the Masterwork for the Graviton Lance however, this is only the beginning as like with any Masterwork you have to complete a set of challenges to actually get the benefits. The challenges : There are 2 challenges to complete for the Graviton Lance. 1. Just kill enemies with the weapon and 2. Get kills using the Graviton Lance's secondary explosion. Some more info: The basic kills challenge is very easy and not too hard to complete however the amount of kills required using the secondary explosion is pretty difficult. The kills in PvP will raise the percentage quicker than PvP but, it for those who aren't really keen on PvP sticking with Kills in PvE is safer and maybe slightly easier Some Tips for the second challenge: The quickest I found to complete this step was to go to mars and find a session where I'm alone and constantly starting the First round of the Escalation Protocol where that huge group of Thralls spawn. Simply wait for them to group and destroy them. Normally this will grant two or three percent at the minimum. I hope this helps anyone struggling to find a place to grind out the challenge. Hope this was helpful.