Go into the temple of altars and place all the books onto the pedestals than hit the switch. Now move onto the center of the star and head down into the catacombs.
Down here the monks will welcome you since you are wearing your monk robes. None of the catacomb inhabitants will harm you, in fact, so keep it that way for now. You can also find gun parts scattered about. Head downwards and here you'll come to the first real puzzle of the game.
Hit the switches in this order to pass:
1. Brown
2. Orange
3. Red
4. Brown
5. Red
6. Blue
7. Yellow
8. Green
9. Yellow
Now you can move onward to the store room, which holds plenty of barrels and a TON of gun parts. You should be able to finish the gun part quest by visiting here.
Now go through the dungeon and you'll eventually see the Nun surronded by five different barriers. Go down each of the colored paths and talk to the silent monk brute's, each of who will give you an item. Use that item on the device nearby to take down the barrier.
You can now talk to the Nun, who will tell you that she controls the powers of the five gods that you learned about from the tourist-monks. She'll than turn into each of the gods, or rather make the statues come to life.
Now we have a choice, we can either fight the statues or talk our way out of it. Talking our way out not only saves us a fight, but it makes the Nun weaker in the end.
The first statue, Beatrice, will knock all your weapons out of your hands. I recommend using the fire axe 2 to continually hit her, and when it happens just run up and pick up the fire axe to continue hurting her. After she's dead you will have all your weapons again.
To talk your way out of it, just answer: "Nine years of work couldn't capture it's perfection."
The next statue, Lucy, will hit you taking away money. Smack her through your wallet pains as fast as you can. To talk your way out of it, just answer: "I give all that I have to the downtrodden."
The next statue, Susan, will slow you down and poison you. She's not too bad, honestly, just block when you need to, use your justice, and smash her to bits. To talk your way out of it, just answer: "That which makes flowers bloom and birds sing."
Albert, the next statue, will make you run away from it... and sometimes will shrink you. He is also resistant to fire and has a very weak projectile attack, so use your ranged weapons. To talk your way out of it, just answer: "The last thing you ever lifted."
The last statue, Walter, will randomly make all your items move to different slots, but he hits like a girl and your items will go back to their original slots after a little while, making Walter no challenge at all. Plus, I mean, you can SEE where your items are so just look and hit whatever button your weapons pop up on. To talk your way out of it, just answer: "I'm confused."
After going through all the gods, the Nun will start to fight, using her ruler as a weapon. Hit her with your best weapons. She's not hard at all since you talked your way through the gods, maybe requiring one potion throughout the fight, and afterwards you'll recover the thong of compassion and be treated to a cutscene. You'll also get the gate key to the west. Nice.
Notice, the Nun will be harder depending on how many gods you fought instead of talked to, as she will inherit their special attacks, so best to talk your way through.