From Destinypedia, the Destiny wiki
A Treasure Map was an item sold by Cayde-6 in Destiny 2 in exchange for Glimmer. Five were offered each week for a specific Destination. Purchasing a Treasure Map added an Ace of Spades icon to an area's map in the Director which denoted the location of one of Cayde-6's secret treasure chests. Loot from these chests could vary from gear to items that could be traded in to Cayde for Glimmer or other rewards. With update 2.0, Cayde and his inventory was removed from the Tower and Treasure Maps can no longer be obtained.
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