The entrance to The Vestibule is located at the bottom of The Obelisk of Lost Souls at Loc ( -524, 409, 385 ) /waypoint -524, 409, 385. To reach this location you must kill The Labyrinth Shadow to open up the second part of the maze then complete a ring event to kill The Keeper of Nihility. After that you can reach the entrance to The Vestibule by opening doors as necessary.
You can zone in and open the first (sealed) door without completing the access quest but you need to finish the access quest List of Acquisitions for the Continuing of Research to get past the second door. The first sealed door is opened by killing Hykor.
You can get an unconscious goblin for later from the sacks next to the vestibule entry door (downstairs door) to avoid having to go back to Runnyeye again next time. If you haven't done the access quest yet, you can't interact with the sacks.
When you enter the Vestibule, you have the choice of going left or straight. Go left, where there are two 44^^ shadows down the stairs. Clear them as they have been known to add through the walls for a fight later. The door at the end of that passage is locked for now.
Go back and take the straight passage. At the end of the passage there is a two level room with two groups of lvl 50 mobs, either 4 no-ups or 2 ^s.
Be careful while fighting, as the encounter from down in the pit will easily add.
There are also 3 lvl 35-42 solo mobs around the room, but they are not aggressive.
Clear the placeholders in the room until The Medium of Hykor, a lvl 50 ^^^, will spawn with two adds.
The Medium has a single target divine damage nuke, for up to somewhere in the 2000 range, that he uses about every 40 seconds to 1 minute.
After you kill the medium, the door at the end of the other passage unlocks. Go into the room and look right. There is a bag in an alcove on the wall you can search. Click on the sack and take six unconscious goblins. Then place one on each of the six tables.
When a goblin is on each table a non-attackable shadowed man will spawn behind a table. After 2 minutes the shadowed man will die and the goblin will come to life.
The goblins are 38-42^^ and have 2 non-linked adds.
When you kill the goblin, another shadowed man will spawn behind another table and the 2 minutes cycle repeats again.
When you kill the last of the 6 goblins, a lvl 49^^ named will spawn (Bovauk or Malisient) with 2 adds.
The information below has been verified with in-game data and the information on this page is correct, even if it looks stupid or makes no sense.Fact: You do need to complete the access quest to get past the second door. The sacks in the alcove can't be interacted with otherwise.