Altars of Reflection
From Destinypedia, the Destiny wiki
Altars of Reflection are a collection of missions that released alongside the The Witch Queen and are playable through the campaign. The missions follow The Guardian bringing a piece of Savathûn, the Witch Queen's past to study in the Altar of Reflection in order to glean insight into Savathûn's plans. There are four missions, three of which are unlocked through the campaign with the fourth unlocked via the Evidence Board. After the initial completion of each mission, they become re-playable with a pinnacle available from them every week.
Story and Background
The first mission to take place chronologically is Altars of Reflection: Pact which takes place during the fifth mission, "The Mirror." After the Guardian retrieves Sagira's shell from the confines of the Temple of the Wrathful, they get a tip from Ikora Rey that The Hidden have found an area with strong concentrations of psychic energy and they may find the answers they seek there. The player locates a portal in the Witch's Echo and after warding off a band of Scorn, enters to find themselves transported into a strange pocket of space where the mission would start.
The second mission to take place is Altars of Reflection: Insight which takes place after the strike on The Lightblade. The Guardian retrieves one of the Tablets of Ruin from the temple to Oryx, the Taken King and brings it to the portal once more.
The third mission and final mission to take place in the campaign is Altars of Reflection: Choice which takes place after the mission "The Last Chance." After retrieving Savathûn's Worm during "The Cunning," the Guardian is rejected from the portal and is tasked with obtaining a different relic and try again. The Guardian fetches a fragment of Savathûn's crystalline prison from her imprisonment with the Awoken and returns to the portal, which lets them in.
The fourth mission, Altars of Reflection: Catalyst is part of of obtaining the Exotic Quest for one of the Exotic Glaives, Edge of Action, Edge of Concurrence, and Edge of Intent. It is part of the mission "REPORT: ALTAR-REFLECT" in which the Guardian opens a portal into this pocket of space through solving a puzzle in a Lost Sector, which is how these quests are accessed when repeated.
The introduction to the mission has the player complete a puzzle to open the door ahead of them, which is locked.