I've found one recently and was wondering how many people had one. It would be nice to know if I'm like 1 in a million or something like that.
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You get it from killing a sword of Crota knight that spawns on the earth or moon, it's a rare drop though so it may take you awhile to get it. Keep playing the first mission from the dlc (update yesterday brings it back as a playable mission) and just run past omnigal and there's a sword bearer in there, kill him and then wipe if you don't get it and repeat.