EX. at Level 15 Devrim Kay you can purchase an upgrade worth 300 Dusklight Shards (Sounds pricey on paper), and a couple thousand Glimmer to give you a permanent buff that rewards a chance to gain Dusklight Shards on Precision Kills on the EDZ
Gives them meaning that could be neato burrito
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I think a subject similar to this about planetary vendors came up back during Year 1. I believe it's the reason planetary vendors sell gear that requires you to have picked up a certain number of reward packages before you can purchase them today. Someone made a mock-up of what the vendor menu could look like and later Bungie made some small changes to the vendors. It hasn't really been expanded on since, hence the requests for vendor updates.