Siege on the Dragon Cult

Overview
When approaching the entrance of Forelhost, Captain Valmir who has set up camp outside in the courtyard, start a conversation with the Dragonborn. He asks for help to retrieve a mask for him inside the tomb. The mask he is reffering to is a Dragon Priest Mask known as Rahgot. He also, as an optional task, asks them to find Skorm Snow-Strider's Journal. Follow the captain to the entrance and the quest starts.

Objectives

 * Obtain Rahgot's Mask
 * (Optional) Find Skorm Snow-Strider's Journal
 * ​Return to Valmir
 * Kill impostor Valmir

Quick walkthrough

 * Speak to Captain Valmir to begin the quest.
 * Enter the ruins of the stronghold Forelhost.
 * (Optional) Find Skorm Snow-Strider's Journal.
 * Make your way through the first zone into the Crypt.
 * Either pick the lock on the well, or find the key, and move on to the Refectory.
 * Travel through the Refectory, find the Glass Claw, and locate the dragon claw door.
 * Use the claw to enter and defeat Rahgot.
 * Return to Valmir with the mask.

Captain Valmir
The Captain can be pickpocketed before entering to find "Valmir's Orders" (or they will get these orders at the end of the quest), and find out that Captain Valmir is an impostor. The orders read:

"You will proceed to the ruins of Forelhost to retrieve the Mask from the Dragon Cult there. If you are discovered, impersonate an officer. It is unlikely that anyone from Skyrim will be clever enough to see through the disguise. Once you have obtained the Mask, bring it to Labyrinthian."

Forelhost Stronghold
Enter and proceed into a large room with a dead Imperial and soon a Dragon Cultist will appear, ready for battle. Dispose of him and follow the marker and then turn right. Beware of traps on the floor and more Dragon Cultists who will appear along the way. Turn right again and go up the stairs, when passing a corridor on the right, a swinging blades trap begins to move. Use Whirlwind Sprint to get pass them.

Inside the next room the Skorm Snow-Strider's Journal will be on a table. Pick it up after the two Dragon Cultists who appear are disposed of. Reading the journal will give a hint of what happened here a long time ago. Continue through the doors on the left and pass a large bedroom, walk to the left again through a door and enter a large area overlooking a room with another Dragon Cultist. Proceed down the ramp, through the dining area and turn right into a room with a ramp where two Draugrs, or Draugr Scourges or Draugr Scourges are waiting in their coffins. (depending on level). After they are disposed of, walk up the ramp to get to the chest but beware of the trap.

Continue through the door on the right into a corridor with burned corpses and then turn left. A draugr (leveled) will be waiting in front of the door to Forelhost Crypt.

Forelhost Crypt
Walk along the corridor and at the end is a way to the left with a cage and a masterlocked door and a swinging blade trap, and a way to the right. Go the way to the right, pass a burial chamber before coming into a circular room leading into the crypt area where Draugrs of different levels will be encontered in a large number. There are also several traps on the way, such as floor plates, rigged chests, swinging axes, magical runes, and soul gems that shoot fire, frost or lightning and it can be hard for a lowleveled to overcome all these and the enemies. If on a higher level there will be more enemies to fight.

Continue through the door on the right into a large area with several levels. Three Draugrs (leveled) will emerge from their coffins as soon as the area is entered. Try to sneak up the ramp before they notice and dispose of them easier. Then collect the loot and in the chest by the coffin there is the Forelhost Well Key mentioned in the journal. Walk back up and over the bridge, jump over the gap to get to the chest standing there before going higher up. Shot down the soulgem trap if possible before passing and continue to the barred door.

Go back through the circular room to the corridor where there was a way to the left with the swinging blades. Pick the lock on the cage and walk down the circular stairs. The stairs ends under water, swim along the corridor to a large cave where one dead Frostbite Spider and a few Skeevers are. Continue on the right. again under water into a room with a note on the table. Go through the door, beware of the pillar trap just inside. Leveled Draugr will awake as soon as entered. Walk through another crypt with several dead draugr and enter Forelhost Refectory.

Forelhost Refectory
Walk up the stairs and face some more leveled Draugr, at the end of the short corridor are a pair of Ebony Gauntlets on a pedistal in front of a large carving on the wall. Removing them sets off a dart trap. Go back and through the iron door into a large room with tables, a gate and several draugr.

To access the balcony on the right side, go through the door on the left and follow the corridor and enter a room full of growing plants and a note with Orders on the table. Three Draugr will emerge when entering, defeat them and proceed up the stairs into an alchemy lab. Beside a dead draurg on the throne chair is Rahgot's Reply, then go upstairs and to the right and enter the next room. Beware of a lightening soul gem trap when going in, on the right is the balcony where a draugr is waiting.

Try to disarm the trap with an arrow and continue round the corner into the library like room where the Glass Dragon Claw is on the right. When picked up the spear-gate will open. Continue up, through a wooden door to enter a room with an Arcane Enchanter, fight the enemies and leave to enter the Dragon Claw hallway. Activate the keyhole (fox, owl, snake) and walk up the stairs into the last chamber.

Finale Battle
When the Dragonborn reaches the top of the stairs, several Draugr Lords will emerge and the coffin containing Rahgot opens. When engaging in battle the dragon priest will rise and use his Dragon Priest Staff. After defeating him and the Draugr Lords, pick up the Rahgot Mask, the staff and the Forelhurst Ritual Chamber Key and go through the large door outside to the Word Wall to learn part of the Storm Call shout. Return to Captain Valdir.

End of Quest
Either jump down to the courtyard where the Captain is or go through the tomb to pick up any loot first if missed when going through the tomb.

The Captain will be engaged in a conversation to either a Stormcloak or Imperial soldier when you get close, revealing himself to be a Stormcloak or an Imperial officier (depending on which side you are on in the civil war, if not chosen yet he will be an Imperial). Stumbling over his words, both men draw their swords and attack, as soon as Valmir is dead the quest is completed.

Notable Loot

 * Rahgot Dragon Priest mask
 * Dragon Priest Staff
 * The entire four-piece set of Ancient Nord Armor worn by the ghosts of the Dragon Cult, who appear as transparent Draugr.
 * Ebony weapons (leveled)

Mining

 * Gold Ore Vein
 * Quicksilver Ore Vein

Trivia

 * Captain Valmir will say, "Return to me once you've obtained the staff," even though the objective is to obtain Rahgot's mask.