If any of you have an Exotic Catalyst that requires lots and lots of kills, I advise going to the Thrall Pit under the Green Room in The Whisper mission. Took me 2 runs in there to masterwork the Sunshot.
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If you're on PS4, just adjust your system's time clock and keep activating escalation protocol. Once the shadow rifts spawn, reload into the same instance and start again. Gather up lots of thralls and just fire away. This is useful for those who are farming Heavy weapon catalysts, Sunshot, or Graviton Lance.