From Destinypedia, the Destiny wiki
Seraph Bunkers are underground defense bunkers created for the Seraphs as part of Rasputin's system-wide resources; which had since been defunct until several were found and made active by the Guardians in the EDZ, on the Moon, and on Io. They were previously active and accessed by Season Pass owners during the Season of the Worthy.
When you land in one of the Seraph Bunker locations, an opening in the ground can be seen. Enter the opening and eventually you will find the Seraph Bunker.
When you first enter the Bunker, there is another opening into the main part of the Bunker. Here, you will find a console that is operated by Rasputin. Here, you can buy Bunker upgrades, Bounties, and other bonuses. There is also a Frame that collects Destination resources if you have the upgrade.
Upon daily reset, a mission known as the "Daily Bunker Buster" is available, filled with enemies, Champions, and a Boss. You must complete the Daily Bunker Buster to buy Bunker upgrades. With Season rank 32, players can purchase Point Defenses, which will automatically complete the Daily Bunker Buster for the following day, the day of purchase, or the rest of the week, for a fee of Encrypted and regular Warmind Bits.
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