Online:Chateau of the Ravenous Rodent (quest)

Quick Walkthrough
# Talk to Valaste at the Mages Guild in Baandari Trading Post (Malabal Tor), Sentinel (Alik'r), or Windhelm (Eastmarch).
# Enter the Shivering Isles.
# Talk to Shalidor and Sheogorath.
# Visit the Chateau Guesthouse and evict the guest who doesn't belong.
# Tour the Darkened Maze and improve the ambiance.
# Meet the family in the Ancestral Manse and play with the family heirlooms.
# Deal with Uncle Leo.
# Collect the book and return to the Guild.

Detailed Walkthrough
After you are directed to Valaste, talk to her to get her to open the portal to the next book. She seems weary from her tasks thus far.
:''"Shalidor found you, excellent. I've puzzled out the hints from that last book … and I'm afraid the news isn't good. Your next trial is in a particularly nasty part of the Shivering Isles. A place called the Chateau of the Ravenous Rodent."
:Should I recognize the name?
:"Not unless you've spent your life poring over obscure Daedric tomes. The Chateau is in the darkest part of Dementia, the shadow land of the Shivering Isles. I'm worried that …."
:Valaste, are you all right?
:"I'm … I'm fine adept. I'm just tired. It's become very draining to translate these tomes. Don't worry about me. I can open the portal to the Isles for you straight away. If you'll allow me?"
:Thank you, Valaste.
She opens the portal, but is visibly drained from the experience. You can talk to her, but she brushes off your concern and directs you to the Chateau of the Ravenous Rodent.

Once you enter, Shalidor will be waiting for you. He calls you over and begins to plan how you will solve this next puzzle, but he is interrupted then Sheogorath appears from a cloud of butterflies.
:Sheogorath: "Not so fast there, Shalidor. Only invited guests at the Chateau. We have standards, you know."
:Arch-Mage Shalidor: "Damn you, Mad God!"
:Sheogorath: "Don't let the door hit you on the way out, Shally."
:Sheogorath: "Annnd ... off you go!"
Sheogorath casts a spell at Shalidor and he vanishes in another cloud of butterflies. With Shalidor out of the way, Sheogorath calls you over to explain your task.
:"Ahh, my little mortal. I'm a man of many personalities, but I tell you what? They're all very fond of you."
:What's the game this time, Sheogorath?
:"The game is  . Or a leg. In fact, all manner of severed limbs. But don't worry about that! I've brought you here because I've been watching you. You work too hard! You need a nice little vacation."
:A vacation?
:"Of course! This is my chateau! It's me family's estate. Gets handed down from me to myself, and so on, and so on. I think you'll love it here. Or hate it. Or one of the two, certainly."
:All right. What's first?
:"Up the road behind me is our guest quarters. But, silly me! All three rooms are already occupied. Frankly, they've overstayed their welcome. One of them, though. Hoo! Just not fitting in. Could you do me a favor? Could you tell them to shove off?"
:What's the catch?
:"Catch? Such an untrusting soul. If there were a catch, I'd say it's that two of my guests are murderous cannibals. My advice, Don't let anyone eat you. If anyone tries to kill you, kill them right back!"
:I'll keep that in mind.
He vanishes, leaving you to enter the mansion alone.

Once you enter the Chateau guesthouse, you will hear Shalidor trying to give you advice.
:Arch-Mage Shalidor: "Be wary. Talk to these "guests" carefully before you try to throw anyone out."
:Sheogorath: "I can hear you, Shally! Don't bother my guests!"
:Arch-Mage Shalidor: "You're the only one who thinks you're funny, Mad God!"''
There are three barred doors in the room. Each one allows you to listen to the person behind it to decide who doesn't belong.  Who is behind each door may vary.

Only the man who threatens to take you to court seems not to have lost his sanity, so you can choose to evict him.
:Noble: "Fine, then! My advocate will be contacting you about this!"
:Noble: "I'll show myself out. But I'm not taking that dreadful portal!"
:Sheogorath: "That's a perfectly good portal. I should know, I made it!"
With that task complete, enter the portal above the fire pit to exit the guesthouse. Sheogorath appears in a cloud of butterflies slightly up the path. He gives you the next task: navigating a dark maze.
:"It's been so long since we had guests. You would have loved my old uncle Leo, back in the day. Charming dinner conversation, when he wasn't bringing up old girlfriends. Literally. Regurgitating them. Nasty habit."
:I evicted your guest. What's next?
:"Well, let's see. Now that you're settled in, you should tour the grounds. We have this lovely maze at the chateau. You simply must see it."
:So I have to navigate a maze? Why?
:"Why do I need a reason for everything? Mortals, mortals, mortals! Always needing a reason to do things. For example: people like to think that light chases away the shadows! I prefer to think that without a few lights, there'd be no shadows to enjoy."
:So the maze will be dark, then?
:"Jolly good, you're getting it! I knew if we spent enough time together, you'd start to think like me. I have that effect on people. It's a bit too dark, actually. Why don't you light a few braziers as you go? Improve the ambience."
:Whatever you say.
:Sheogorath: "Mind what bumps in the night, now!"''

Enter the maze ahead, and you'll notice the darkness ramps up significantly. Your task is to simply follow the markers and light the "Cold braziers" while avoiding or killing the shadowy "Bump in the Night" enemies (spider, giant bat, and werewolf forms) in the maze.

Once you finish the maze, Sheogorath is waiting for you at the end of the path to give you the next task.
:''"So ... what did you think? What was your favorite part? No, don't answer that. I can see by the look on your face how happy you are!"
:I made it through. What's left?
:"Such confidence! Braggadocio! Gumption! I like that! The last place I'd like you to visit is our humble little manse. Just behind me."
:That's a mansion?
:"I want you to meet the family! So many fond memories. There was that one time, with the scalpel? And all of our family dinners. hah! And of course, you'll get to play with the family heirlooms!"
:Heirlooms?
:"Aye! We have an old rhyme about them. Ahem: "Four lights in a row, poke one to make it glow." No that's wrong. Maybe it was "Four lights in a trough, poke one to turn it off?" Hmm. Something like that."
:I'll be sure to remember that.
He disappears again, allowing you to enter the door behind him. Inside, several hostile madmen and madwomen are milling around and attacking as you follow the path through the manse. At the very bottom, you see a door with four crystals before it. Some are lit and some are not; the lit crystals are connecting a beam of energy with the door.

Your task is to light all four crystals. Each one you activate will flip it from off to on (or vice versa), but also flip the ones directly next to it as well. Once you manage to light all four, Sheogorath will appear again in a cloud of butterflies to congratulate you.
:"Isn't it beautiful? The most beautiful part of the chateau. You can see why I've held onto the place all these years."
:It's great. Can I have the book now?
:"Now just hold on there. Haven't you been wondering why it's called the Chateau of the Ravenous Rodent?"
:I guess?
:"Well, you should! And before I give you the last tome—before I reward you and Shally for all your hard work—you need to meet one more member of my family. Let me tell you the story of old Uncle Leo.
After he tells you the story of how Uncle Leo is now a disappointment to the family, he tells you to enter the master bedroom and kill the Flesh Atronach. It's a fairly standard fight, and Sheogorath will be waiting at the starcase above when you finish.
:''"Always sad to see a good man die. Leo's death, just now? Hilarious! Hah."
:I've toured the Chateau. May I have the book now?
:"I should make you fight Narwhals on the open ocean. I should make you run a gauntlet of angry Argonian concubines! But I won't. Book's yours."
:Thank you.
:"Yes, yes. Well, I'm sure you and Shalidor will be very happy with your new book. Of course, Valaste has been the one doing all the reading, right? Send her my best. And tell her to read real close on this last one."''
He vanishes in another burst of butterflies and leaves the book on the pedestal nearby. Take it to be returned to Valaste and receive your reward.

Notes
Heirloom lighting puzzle: Correct sequence from left to right is 1, 4, 2, 3, 1. 

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