Stackable effect that increases the chances the next Ultra you defeat or Crucible match you complete will award an Exotic Engram.
― In-game description
Three of Coins is a consumable that, when used, provides a chance that a Guardian will receive an exotic engram after killing an Ultra or completing a Crucible match. If an exotic engram is not dropped, the Guardian can use another Three of Coins, and the chance that the next Ultra killed or Crucible match completed will yield an exotic engram increases.
Player trials show no increase in odds of obtaining an exotic engram when consuming multiple Three of Coins before the buff is consumed; therefore, optimal usage is one Three of Coins per Ultra kill or Crucible match. The following table illustrates an analysis of the odds of obtaining an exotic after consecutive Three of Coins consumptions:
There is a hidden cooldown period after using a Three during which using additional Threes will not increase drop chance in order to prevent exploitation of easily repeatable ultra kills. The exact length of the cooldown has not been stated, but it is believed to be between 10 and 15 minutes.