Folgunthur

Located southeast of Solitude, this ruin contains one of the fragments for The Gauldur Amulet. The quest to obtain the fragments can be started here if it wasn't initiated during Under Saarthal. Right near the entrance is a medium sized camp, indicating someone has been in the ruin before.

Walkthrough
The first part of the ruin has already been opened by Valen's expedition. Bodies of unfortunate adventurers and some dead Draugr litter the entrance. Also in the first room there are 8 pillars four having the combination that unlocks the room to the right having a chest that has some nice loot in it. The skill book Fire and Darkness can be found on the ground level of the first main room near a dead adventurer. At the top of the bridge you will find Daynas Valen dead, with the Ivory Dragon Claw near or on his body. Place the claw in the socket behind Valen's head to activate the drawbridge. To get past the two iron gates pull the fist lever on the left then the furthest lever on the right.

You will enter a square room with a rounded grate in the middle covering some spiral stairs with a fire pit in the bottom middle. Be careful when entering this room, there are two Draugr sitting propped up in two throne chairs with two levers located directly next to each throne. To the right of the first throne there should be a walkthrough entry into another room with 2 Restless Draugr and 3 symbols for the room that is adjacent, accessed by pulling either lever by the thrones in the room prior. The far throne has a switch behind it that opens up into an area with a leveled Draugr, defeat him and there will be a set of rotating stones which you will use the sequence combination found in the first secret room (Eagle->Whale->Snake). Each stone must be facing a different wall. For example: the first pillar (snake) must be facing the wall of the door you just entered. The second pillar (whale) will be facing the wall directly to your left. The final pillar (bird) will be facing the wall containing the two upright coffins -- directly across from the door you entered. A Black Soul Gem will be on one of the Draugr in either of these rooms, it seems to depend on what level you are at at that time. (I went through the dungeon early on and didn't find any, but had to reload and did the dungeon on at a higher level and found 2 Black Soul Gems).

After leaving the room, enter previous area and pull the chain that is hung directly across from the thrones. This will open the metal grate and allow you to proceed down the stairs. If you pull the chain without the proper combination in place, then a dart trap fires.After down the stairs there should be a random two-handed weapon to the right hidden partly in the water. Kill the two Frostbite Spiders in the corridor and in the next room you will face 3 Draugr and 3 Restless Draugr in any order. Prior to the room with the draugrs, look on the shelves for leveled Armor.

The final room combination. Look at the Ivory Claw in your inventory. On the back of the claw is the correct solution to the circular door (t-b: dragon, bird, bird). After entering Folgunthur Crypt you will be faced with Mikrul Gauldurson, a powerful Draugr Lord and son of Gauldur. Once defeated, take his piece of the amulet to continue the Forbidden Legend quest line. If his body is unlootable for any reason, simply use the 'wait' command for a few hours and it should resolve, or exit and re-enter the room. One technique for killing him is to ignore his thralls and simply go straight for him, as once he is dead these thralls will fall dead.

To exit this room, use the Ivory Claw on the right side door (a circular pad on a stone to the left of the door contains a spot to use the claw key). In the next room you will find a Word Wall with one of the words for Frost Breath, depending on how many words for that shout you already know. It is also worthy to note that if the player loses, or sells, the Ivory Claw, (after the quest, it becomes nonessential) and wishes to learn the Thu'um, the "wooden bowl glitch" can be used to pass through the bars, without the claw. Afterwards, enter Folgunthur and proceed until you are in a sarcophagus and hit the appropriate button (depending on you platform) to push the door open. Jump down and turn right and use the chain on the right of the gate to open it. In the last room on the way out is a hidden door which can be opened with the ivory claw, containing a chest.

Enemies

 * Leveled Draugr
 * Leveled Frostbite Spider
 * Mikrul Gauldurson

Notable loot

 * Dragon Claw: Ivory Dragon Claw
 * Skill Book (One-Handed): Fire and Darkness
 * Rare Item: Black Soul Gem
 * Unique Item: Gauldur Amulet Fragment
 * Unique Weapon: Gauldur Blackblade
 * Word Wall: Frost Breath
 * Quest Item: Daynas Valen's Notes
 * Quest Item: Daynas Valen's Journal

Puzzles

 * Nordic Pillars: Hawk (left), Whale (centre), Snake (right) when standing on the outer arrows
 * Nordic Puzzle Door (Ivory Claw): Hawk,Hawk,Dragon

Bugs

 * If you complete Folgunthor before starting Forbidden Legend (or, at least, before getting the Folgunthor-related objective) you may be unable to obtain the required amulet fragment, and the objective may remain unfulfilled even when adding the fragment with player.additem. It is therefore recommended to leave this dungeon until the appropriate point during the quest.
 * Sometimes the three stones that are copying the other rooms will get stuck so you will have to restart the console and load a save that was before you got in Folgunthur. Alternatively, saving right there in the room and then reloading that save has successfully overcome the bug.
 * Sometimes, when entering the room with two thrones, each with a Draugr, two doors, and two levers, the right door will not open, nor is there any way to open it. No known cause of this.
 * After defeating the Draugr Lord and now on the way out there is small hallway with the fire trap leading back out where you came before to the beginning of the dungeon. It has a gate at both ends. The far one however when closed seems impossible to open. If you create a new save near this area, quit, then reload the new save, the glitch should fix itself. (Failed; tried that multiple times and the gate still remained closed. Had to restart to the last save before I entered.)
 * (PS3) It appears submerging yourself into the water in Folgunthor will freeze the console.

Gallery
Фолгунтур