This coin is granted once reaching a high point in the Crucible. It grants you a trip to Mercury where you have to win three times in a row, but if you lose all three you can NEVER (probably not) play it again. However each time you win it grants another try, the reward for winning is becoming and ELITE crucible Guardian. With some epic gear.
http://imgur.com/gFErBZU
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Not true the event will go in and you can but in with a strange coin that is from bungies mouth were time you lose and don't get three in a row ya gotta spend another coin to try again