Head to Volunruud, and read the book (found in the first room) to start the quest. Fight your way through the halls and find the two weapon replicas needed to open the puzzle-door. The boss can be difficult, so be prepared.
Following the linear path, the first room you come across holds the book Heddic’s Volunruud Notes and what appears to be Heddic’s skeleton. To the left is a skeleton sitting on a throne, that will come alive and attack you if given the chance. Reading the book begins the quest.
The next room branches off into several directions, one of which lead up to the puzzle-door and the final chamber.
First, head through the Southwest passage to find a chest and some loot. There’s nothing else, here, so head back and through the Northeast area.
Head on through to the next room, and there will be several more undead waiting for you scattered around. Take care of them, and head down past the swinging spike trap. At the next fork, take a right. When you get to an altar with an ancient Nordic helm, there is an undead in a coffin to your hard right. Continue through the iron door and to the first objective, which holds the ceremonial sword. As you approach, however, two final undead will pop out of the coffins behind and attack. Head back to the big branching chamber.
Move through the Northwest door. The first and second bends have undead sleeping in the walls. After that, there are a couple more waiting around the next corner. Head down through the cave and through the next set of iron doors to find the next objective, and an undead boss (complete with lackey) to the right. Take them out, while being careful of the floor traps scattered between them and you. The ceremonial axe is up on the wall on display. Also, grab the nice maces skill book Mace Etiquette to the right. Now with the two pieces, head back to the puzzle-door and go through to the next area, the Elder’s Cairn.
At first, there is a small camp with a couple of goodies to grab. Up ahead is a room with a couple of undead waiting on either side of an overhead bridge. Take them out, or just run past them, and head to the next and final chamber. This holds the final boss of the quest, Kvenel the Tongue, along with an undead conjurer. Both are very difficult to handle, and should only be engaged at higher levels.
The best course of action is to try and get the jump on the conjurer, and take him out first, stopping his spells and his familiar. You could try a hit and run tactic, where you kill one of them and run to regenerate your health. Additionally, the conjurer uses ice magic and Kvenel has an ice-enchanted sword that will slow you down, so that makes running away or closing the initial gap rather difficult for any melee fighters. Whirlwind Sprint and plenty of stamina is advised. Once the conjurer is dead, Kvenel is simple enough, though still a threat. Do what you normally do to take a melee down and you’ll get him soon enough.
Upon looting his ectoplasmic remains, you can find his enchanted sword, Eduj, as well as all his other belongings. Due to a bug, you have to activate his remains again to obtain Okin, the enchanted axe. Around his throne room are various potions, so make sure to grab them all. Head towards the right, past the throne room, and you’ll encounter a word wall with a piece of the Aura Whisper shout. A bit further will be the bridge from before, and any undead you left there. Wipe out what’s left of them, and head for a final bit of loot with a Dragon Priest Dagger, and a reference book on the Labyrinthian. Before heading to the exit return to the bridge and look to your right to find a chest. You can reach it by jumping to the tree roots, then jumping again over to the chest. Drop down and head south to find the exit.