"One person from each tribe will be the caller. The rest of the tribe will be blindfolded and paired up. Using only verbal commands, the caller will direct their tribe mates to collect ten items scattered in the field. Once all ten items have been collected, the caller will direct one pair out to find a set of keys. Those keys will unlock a chest. The first tribe to get their chest and all ten items back to the start wins immunity and the reward." ~ @SurvivorWiki
They use the Medallion and give it to the other tribe.
The advantage is that two items will already be placed onto their tribe mat, thus reducing their required number of items to eight.
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They also win a toolkit, a tarp, a rope and a knife, fishing gear, a collapsible chair, and a grill!
Proceed to tribe events.