This ancient structure was built to harness the power of a star and use it as a weapon. Only by finding and disabling its generators, can it be stopped.
Star Cathedral is a timed mission. Initially, 24 minutes are given to disable 4 generators located at the far reaches of the zone, with most of the generators being guarded by different midbosses. Destroying the first three generators adds 2 more minutes each to the remaining time and destroying the last generator stops the timer entirely, starting the transition to the mission boss fight. If time runs out, the screen fades to white and all player characters are kicked out of the zone without killing living shells.
Star Cathedral cannot be accessed at will. Rather, a portal to Star Cathedral only opens when sufficient quantities of zone keys have been deposited into the crystals on the monolith to the left of the Eschaton shop:
As of version 1.2, the portal will stay open for 20 minutes, and each player will only get to enter a portal once - homing out of a Star Cathedral will lock you out of Star Cathedral for the rest of the time that the portal is open.
Midbosses can drop any standard tier five equipment with 1-4 modifiers. Additionally, they can also drop exotic equipment that is normally exclusive to tier three and tier four zones.
The boss can drop any standard tier five equipment with up to 4 modifiers. Additionally, it drops any three (duplicates are fair game) of the following exotic equipment in its death chest: Bombard, Hydra, Fireform, Motley, Kunai, Mimic, Quaestor, Locust, Volta, Scorpion, Blink, Aeonic Empyreals, Frenzied Berserker, Spiked Stompers, Enlarged Blockers.