Guardians grab a team and go into a legendary lost sector and run it on master level. As long as everyone gets a couple of shots on the champions it counts towards the quest. My son and I ran the leg. lost sector on the moon and each run netted 11 champions. In less than 5 runs you are done. In fact we didnt even take out the boss when we got to the last champion and just rinse and repeated.
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If you can do master lost sectors, you can definitely do master ketch crash, & you'll clear the step in one run.