The entry gate should allow any ship that is battlecruiser sized or smaller.
"Previous explorers have commented that one of the gates requires a passkey. Alternatively, it can be bypassed by convincing the commander to unlock it. The overseer guards the Cathedral vigorously."
Room 1
On warp-in, there is a single spider drone. Killing it will spawn a wave of approximately 8 to 10 destroyers, and another spider drone. Killing the second spider drone will spawn a wave of 4 cruisers, and 4 destroyers... and another spider drone. Killing the spider drone will spawn 4 to 5 cruisers, 4 to 5 destroyers, and a Commander battlecruiser. Killing the commander unlocks the warp gate into the second room.
Please note: The destruction of the Militant Commander has activated a mechanism inside the nearby acceleration gate. It now appears to be unlocked.
Room 2
The second room contains a spider drone, 4 to 6 destroyers, and 5 to 7 cruisers. Killing the spider drone spawns another wave of 4 to 6 cruisers, 4 to 6 destroyers, and a spider drone. Killing that wave's spider drone spawns another 5 cruisers.
The Blood Cathedral in the middle of the area will spawn a Militant Commander (in a battlecruiser), 2 to 4 destroyers, and 4 cruisers.
Please note: Killing the commander might trigger an escalation.
Escalation - Medical Twilight
"The slaves you liberated from this Blood facility report that this was a holding place where slaves were gathered, before being sent off to a blood replenishing "medical" station. You have heard about those places; where the Blood members go to get their blood exchanged with the blood of a slave who has been put on a special "blood cleansing" diet for a period of time. Needless to say, this leaves the poor slave empty of the vital fluid in question. Understandably your newfound slaves are quite thrilled with these recent turn of events. None of them knows where this so called "medical" station is, but a couple can tell you that they were in another holding station like this one, before they came here and coincidentally it is not all that far away..."