From Destinypedia, the Destiny wiki
Bright Dust is a currency used to buy applicable items from the Eververse store and the Tribute Hall. They may be occasionally rewarded from Seasonal Engrams. Bright Dust is primarily earned from weekly and additional bounties from certain vendors, such as Zavala, Lord Shaxx and the Drifter. If there is a seasonal event ongoing, and Eva Levante is present, she may offer weekly and additional bounties related to the event that rewards Bright Dust upon their completion.
Because bounties are per character, a soft cap of 3,600 (4,800 if Eva is present) Bright Dust can be earned weekly, as 200 is rewarded per weekly bounty, with 6 (8 if Eva is present) weekly bounties available per character. Additional Bright Dust can be earned through the previously mentioned additional bounties. These bounties cost more than daily bounties but allow for the collection of further bright dust. The limit to said bounties is that they only offer 10 Bright Dust upon completion, however, they can be repeated continuously.
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