Hub 3: Silent Refectory

Walkthrough
The room you appear in is a storage room full of crates that form lots of corridors in a maze-like way. So the first thing you should do, is explore the WHOLE of this big room, killing all the Dark Bishops as you go. Make sure you thoroughly explored the whole of the room - a lot of crates or even piles of crates can be jumped upon, revealing something new.

In doing that, you should reveal three switches. First pull the one in the north-western end of the room (it is hidden behind some crates forming a kind of stairway). Pulling it opens a part of the northern wall of this room, leading first to a small antechamber with a window and then into a big dining room. Kill all the Dark Bishops there. If you want to, you can push the northern griffin wall (just walk against it). It reveals a small niche with a banishment device there. Then open the door in the western wall. It leads to two more doors, the southern one opening on a lava room, the northern one on a water room. Anyway, in both of those rooms there is a wall that can be pivoted (again by walking against it). They both lead to the same room with a couple of Dark Bishops hidden behind windows (these open when you walk near them so that you can take all the goodies behind) and a Ruby Planet on a pedestal. Take it and get back to the central storage room; if you want to, one of the small niches in the lava room opened leading to a corridor that takes you back to the room with crates. Or you can take the way you came, it doesn't really matter.

Now get back to the original crate maze, and pull the switch that is in the southeastern part of the room. This one lowers a pile of crates close to it (in the eastern wall), taking you to a big circular room with a spiraling staircase going around it. At the end of it is a switch. Pull it and go into the dining room north. There, the southeastern griffin wall opened, allowing you to access the corridor that goes around the circular room you've just been in. Again, at its end is a switch. If you get back to the dining room, you'll notice that this time, it is the eastern griffin wall that opened, leading to another big circular room. Kill all the Dark Bishops there as the floor slowly rises and then collect the Sapphire Planet in the center. Be careful, because the platform the Planet is on is actually a fast-descending lift, so you can't run all the way across, and at least the second part of the jump will have to use the jump key. A double jump is easiest. If you steady yourself after the first jump, you can safely ride the lift to the bottom, and back up. You can't get stuck here, because you can always bring the lift down by stepping inside the surrounding square.

Get back to the storage room (the pile of crates can be lowered by being simply used) and there pull the last remaining switch. It is in the southern end of the room. This switch lowers stairs in the corridor-like southern part of the storage room (the part where there are almost no crates). The stairs reveal a portal that is going to take you back to the Heresiarch's Seminary but before going through it, walk behind it where there is a small room with still more Dark Bishops. When you're done with them, get to the end of that room and pull the switch there. This opens the griffin wall right behind you, revealing the Emerald Planet.

If you have all the three Planets, you have finished this level and can take the portal back to Heresiarch's Seminary.