"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 do not use the Medallion and get to keep it.
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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.