Online:Shattered and Scattered

Quick Walkthrough
#Talk to Mirri Elendis.
#Enter Doomvault Vulpinaz.
#Pick one:
##Just break the main crystal in front of Eolaf; or
##Grapple up above on your right to break a linked crystal.
#Talk to the survivors.
#Read the journal and talk to Mirri.
#Rescue or kill Ardia.
#Talk to the survivors.
#Examine Ghalor.
#Rescue or kill Deejos.
#Open the warded door.
#Rescue or kill Liam Elendis.
#Talk to Mirri outside the Doomvault.

Detailed Walkthrough
Mirri is just outside Doomvault Vulpinaz, arguing with Brigadine Andricius of the Ivory Brigade. Wait for her to finish cursing, then talk to her.
:''"Who are you? Another of these useless Leyawiin layabouts? No, you're an adventurer, like me. Don't tell me Xigira roped you into this mess too."
:No, what's the trouble?
:"My little brother and I answered a job posting seeking adventurers to help explore a newly discovered ruin, only once the expedition got underway—and we were all split up—our employers turned on us. I barely got away."
:What's your plan now?
:"Free my little brother and the others before something terrible befalls them. I don't know if I can do this on my own, but I have to try. Can I count on your help? Or were all the questions just morbid curiosity? I can pay if I have to."
:I'll help you with your rescue.
:"There were five, in addition to me who got duped into this. My brother, Liam; Eolaf, a Nord warrior; Ardia, a High Elf researcher; Deejos, an Argonian scout; and Ghalor, a Wood Elf adventurer. Other than my brother, I don't know a lot about them."
:What do you know about the ones who tried to take you captive?
:"Not much. Xigira, the woman who hired us, was charming. I didn't buy her story that her expedition was for study, but she paid half our fee up front. I figured they were just treasure hunters looking for plunder. We had no idea they were a cult."
:When did you realize?
:"About the time they said, don't kill her, we need her for the ritual. And while they were trying to subdue me. Probably saved my life though. I fought twice as hard knowing they were taking it easy on me. No one else escaped, that I know of."
:I'm ready when you are.'''

You can also ask Mirri about the ruin. She identifies it as a Daedric ruin, but notes that it's fairly new&mdash;a few hundred years old at most. Mirri tells you that its age and the fact that the interior seems demolished strikes her as odd.

Once inside the Doomvault, Mirri will suggest you find their base camp first:
:Mirri Elendis: "We need to reach the base camp, but be careful. I saw a lot more cultists during my escape than the ones who led me here."

Proceed north through the metal halls until you find the sky above your head. Mirri tells you it wasn't like this before she escaped. Grapple over to the ledge on the other side of the sulfurous river and investigate the expedition's camp.

As you approach the base camp, Mirri will notice one of her group members:
:Mirri Elendis: "The base camp should be—Eolaf! What are those fetchers doing to him?"

As you approach the Soul Siphon Array, Xigira will taunt Eolaf:
:Eolaf: ''"I don't … I don't feel so good … hurk …."
:Xigira: "Endure, Nord. The foothold is nearly complete!"
: 
:Mirri Elendis: "That voice! Xigira!"

The Nord appears to be strapped to a device and the surrounding cultists are using the crystals pylons to do something to him. Mirri will run up to the rock overlooking the scene, where you can talk about what is happening to Eolaf and what can be done:
:"That's Eolaf! One of the other adventurers Xigira duped with this setup. They've got him strung up like a New Life pony guar. Survey stones, my ashy arse. That's a sacrifice if I've ever seen one! We've got to do something."
:Survey stone?
:"Xigira had us escorting her scholars around the area to place those so-called survey stones. Supposedly they would get the layout of this place in an instant. Bunch of guar dung, clearly. It's sucking the life out of him!"
:Can we destroy it?
:"I damn well plan to try. It'll be dangerous though. For Eolaf most of all. That ritual is already feeding off of him somehow. The sudden shock of destroying the stone might kill him. We could try weakening the ritual before ending it entirely."
:How do we do that?
:"That array by Eolaf seems to be the heart of the ritual, but the magic is being drawn to another focal point nearby. Destroying that might lighten the load on Eolaf, and the backlash of ending the ritual by force. It's the best chance of saving him."
:Understood. let's go.'''

How to Save Mirri's Friends
There is a right and wrong way of saving the explorers.

If you ignore the outer crystals and just go to the middle one and destroy it, the person in the trap will die. You must destroy the outer crystals before smashing the one in the center of the apparatus in order for the victim to survive.

If Mirri's brother Liam dies, it will affect her dialogue not only at the end of this quest, but in future quests.

Eolaf
Looking at Eolaf's situation, you'll notice a small crystal in front of him. A purple trail of magic connected to the crystal leads up to the cliff in front of Eolaf. You can grapple up to it or jump up the hill on the western side of the formation. However you get up there, if you break the larger Ritual Focus Crystal on top of the cliff before breaking the smaller Soul Siphon Array in front of Eolaf, he will survive. If you destroy the small crystal without doing anything else, Eolaf will perish.

Once you kill or free Eolaf, follow Mirri north through a door to the Interstitial Corridor. Talk to Mirri once you're inside. You also have the opportunity to talk to Eolaf, if he survived the ordeal.

:"It was definitely a Daedric ritual, but not your typical sacrifice. Offerings to the Princes are usually quick and brutal. This was much more purposeful. I don't know what they were trying to accomplish, but they were using Eolaf's soul to power it."
:Do you know where the others were taken?
:"The s'wits didn't tell us much of their plans before stabbing us in the back, but I've got a rough idea where they were taking the other stones. If we head out the other side of these corridors we should be on the right path."
:Let's keep moving then.
:"I recognize these corridors. The expedition hadn't split up just yet. Everyone aside from Eolaf would have been lead somewhere beyond. The exit wasn't far, but it's sure to feel like farther now that the place's crawling with cultists and Daedra."''

Ardia
Continue through the door at the other end of the hallway to proceed with the search for the rest of Mirri's companions. You'll come across ''Ardia's Journal at the end of the next area, by the door leading outside. Read the journal, then talk to Mirri.
:"Well, I'll be. Ardia actually made a break for it. She's the last one I'd have expected to escape. Two left feet, that one. Much as I'd like to believe she made it out, somehow I doubt it."
:You think she was caught?
:"Honestly, I'm impressed she made it this far, but my gut tells me she's still here. I think we should keep looking for the rest of those sacrificial stones. Whoever's still bound up in the cult's rituals is in the greatest danger."
:Understood.'''

Head through the door to continue the search.

Grapple across the first gap. You'll make a similar crystal-smashing decision at this clearing, although now there are 2 secondary crystals if you choose to do them: one to the right (east), and one to the left (west). The grapple points are on the east and west side of the path leading up to Ardia. Break the two focus stones on either side of the main soul array, then break the gem in front of Ardia to set her free. Mirri takes Ardia up the path leading north. 

You can talk to Ardia if you'd like, but your objective is to talk to Mirri. Ardia reveals what you probably suspected at this point: Xigira, the one who hired Mirri and her adventuring cohorts, is a Daedra. She drops her mask around her followers. Talk to Mirri.


Deejos
When you reach the third outdoor section, the Core Layer, you will find that the Deadlands has supplanted the area, with only some burnt trees and grass remaining. Mirri recognizes someone nearby:
:Mirri Elendis: "Is that—Ghalor! Over here!"
: 
:Mirri Elendis: "Ghalor? Oh, fetching Vehk!"''
: 

Examine Ghalor. He doesn't acknowledge you, and seems unaware of his surroundings. Talk to Mirri.
:''"He's gone. Soul shriven. I've read accounts of this happening, but I've never seen it myself. This ravaged body is all that's left of Ghalor. His soul … gone somewhere far worse. This is what will happen to the others. To my little brother …."
:Only if we fail.
:"Right. You're right. This isn't the time to lose it. There's still hope for the others. Ghalor couldn't have wandered far like this. There must be another ritual site nearby. Let's go!"''

Mirri surmises one of her adventuring fellows must be nearby. Continue through the doomvault, making your way northeast. Heading up the wooden platform east of Ghalor will lead you up a hill, towards a river of lava. A Ruinach patrols the path leading northeast of here, leading north from this hill. You can also take the path leading west of Ghalor's position and grapple across a chasm with a river of lava cutting through it. No matter which path you take, you'll find Deejos here.

To save Deejos, you'll need to break two focal points. Grapple to the north when Mirri points out Deejos' presence; the first crystal is north of that dialogue trigger. When you break that one, you can head southwest, crossing a bridge, turning left at the end of the bridge and grappling up to reach the next focal point. Once both focal points are down, you can break the central soul array to safely rescue Deejos. Mirri leads Deejos up the path leading southeast. Follow them into the next corridor.

You can talk to Deejos, but you need to speak with Mirri to proceed.

:"Liam … hang in there, little brother. We'll find you. We seem to be getting close to the heart of the cult's plot. Other than the ruins, the terrain here is unrecognizable from where we came from. I'd wager that's where we'll find him. And Xigira."
:You want to go after her too?
:"No. I don't care about that hooded viper. I just want my little brother back … but if she stands in our way, I'll gladly kick her fetching arse back to Oblivion. Come on. Liam needs me."

Liam
Traverse the next area. Fighting your way through Daedra, you will soon reach a gate where Xigira is waiting for you:
:Mirri Elendis: "Xigira! Give Liam back and maybe I won't fetching kill you!"
:Xigira: "Allow me to reward you for hampering our progress. You may listen to your brother's muffled screams unmolested as you stand helpless before this gateway."
: 
:Mirri Elendis: "Damn it! She's sealed the gate! We need to remove that barrier! That switch might have something to do with it."

Xigira has warded the door to prevent your entry. You can ask Mirri for advice on what to do:
:"That s'wit's locked us out! We aren't getting that gate open by force, but I bet that mechanism plays some part in getting it open."
:Any thoughts on what to do?
:"I think that mechanism must be connected to the gate, but that can't be the only thing stopping us or Xigira wouldn't be so confident. We should look around. There might be more of these Daedric objects involved in the barrier."

There are three levers you need to find and pull to unlock the gate. Two are reachable with the grappling bow, on the northeast and south sides of the door (left and right of the central switch). The third is right in front of the door, upon a pedestal. Once you have done, the gate will unseal:
:Mirri Elendis: "I think that did it! The gate's unsealed! Let's find Liam!"''

You can fight Xigira in the middle of the room, but this is optional. In order to rescue Liam, you need to break two crystals south and northeast of the central soul array. The Anchor Stone Array (a sigil stone on a dais, which glows with a dark, misty purple aura) in front of Liam (who you'll grapple up to in order to reach) is what will make or break this rescue: this is the last component you need to break to rescue Liam. If you break this before destroying the crystals down below, Liam will die. Destroy the crystals below his platform, to the south and northeast, before you break the Anchor Stone Array, if you want to save Liam Elendis. 

You can speak to Mirri here. She obviously wants you to save her younger brother.
:''"This is it! We're going to save Liam and stop Xigira's plot here and now. Let's find the ritual's focal points and weaken it so we can set him free."
:You think we have time for that?
:"I don't know! He's my little brother, I have to try! If—if it comes to it … end the ritual prematurely. I'd rather send Liam into the arms of Mother Morrowind than let Oblivion have him. Just, try. Please?"
:I'll do what I can.'''

Once you've broken the Anchor Stone Array, follow Mirri through the southeastern door and talk to her at the camp just north of the vault's exit. You can then speak to Mirri to end the quest. Her dialogue depends on whether or not her brother survived:


After the quest, you can summon Mirri Elendis as a Companion.
  

Quest Stages