Morrowind:Siege at Firemoth (quest)

Quick Walkthrough
#Meet Sellus Gravius at the Census and Excise office in Seyda Neen for orders about Firemoth.
#Team up with Aronil, Hjrondir, and Mara, and take a ship to the islands.
#Fight your way through hordes of skeletons to the fort, then more skeletons, and diseased rats, to the tomb deep below the fort.
#Defeat Grurn, a powerful Lich, and retrieve the Ward of Akavir.
#Return with this shield to Sellus Gravius for your reward.

Detailed Walkthrough
Starting the Quest
To start, talk to Sellus Gravius at the Census and Excise office in Seyda Neen. Ask him about "Firemoth", and he will set you up with a ship and a crew to sail there and retake the fort, which has been overrun by the undead for some time. Then head out to the docks, where you will meet Aronil, Hjrondir, and Mara. Don't get too attached to them, as the odds are pretty good that they won't survive this mission. Once you've introduced yourself, talk to Silm-Dar, the Argonian shipmaster there, and he will take you to the island (or you could just swim, Water Walk, or Levitate there and do it all on your own, or do some of it and swim back for the help). If you take the ship, any other follower NPCs will be left behind (including the Shock Centurion you can get as a high-ranking Telvanni, and Fjorgeir, the Fighters Guild man you can hire in completing stage three of the Hlaalu player stronghold).

The Islands
When you arrive, you'll find yourself on the northern edge of a circular ring of islands. Go either direction around the ring, and you'll soon start running into hordes of Skeleton Warriors. If you brought the three companions with you, they will follow the usual tactic of diving headlong into battle without any thought for strategy or self-preservation instincts. Aronil will probably last the longest, given that he is a spellcaster and won't get into direct combat right away. Mara is technically an archer, but she is only armed with an Ebony Longsword. There's not much you can do about Hjrondir other than try to keep up. Might be a good idea to have some Restore Health on Touch/Target effects available through spells or items. There are lots of skeletons (many of them archers) on these islands, and more in the keep, so you'll need to pack a good supply to last through them all. Strong area-of-effect spells can take out multiple archers at one time. The Keep is on the southern edge of the ring, so either direction you go will work. If you take the western side of the ring, you might find a secret entrance which skips half of the dungeon, but you're also missing out on a lot of good loot, so it's your choice. If you plan to do the entire fort, the eastern route is easier, in that it provides flat areas where groups of skeletons will charge from a distance, giving you time to use ranged attacks, especially if you have seen them and the companions have not yet (and thus have not gotten between you and the skeletons). Do not do "Dispose of Corpse" on the skeletons if you don't want to fight them all again on the way back. Or you can take the eastern route and go in the front, then go out the back dungeon entrance and go around the other side of the island ring, if the skeleton army has respawned.

If you intend to keep all three companions alive and have sailed with them, this is challenging, and not practical except for high-level characters who can cast spell after spell while shrugging off assaults from multiple archers and your own spellcaster ally. (It's also arguably what makes this quest fun at all for such characters, since the monsters and loot are not leveled – there aren't even any Skeleton Champions. This quest appears to have been written with level 5–10 characters in mind.) Aronil casts Shockball, a lot, with no regard for who may be in the way, including you and his two comrades.  Mara (who is really rather weak for a mission like this) will often die from this friendly fire in the very first engagement.  One strategy is to cast Calm Humanoid on her periodically to keep her out of the fight, and to cast Restore Health on Hjrondir frequently, and leave most of the fighting to him and Aronil. Unlike with Calvus Horatius, you cannot access these companions' inventories to give them healing potions or better gear, nor can you order them to wait while you go ahead. Another strategy is to leave Aronil behind with a Calm, and do most of the fighting with the other two.  A different approach is to stay in deep water as much as possible and return to it, leading the skeletons into the sea for swimming melee (but note that the companions do not have water-breathing ability, so keep it at the surface, and listen for drowning sounds). If you have the Boots of Blinding Speed or another way to greatly boost your speed, you can also simply outrun all the companions quickly on land and do most of the fighting yourself.

The Keep
The Keep itself is relatively straightforward. If you approached from the east, you'll first see two guard towers out front. There's very little of value in them, though they do provide a good respite from fighting if you need to recover, as there are no enemies inside. However, do not use the Rest function if you want the companions to continue with you. Doing so may break their follower scripting, such that they just stand there as regular NPCs.

The exterior of the Keep is guarded by many archers on the walls, so you'll want to run in fast to take them down. You could try archery or magic to shoot them from the ground, but there's a lot of them, and they have advantage of numbers, plus you've got three relatively stupid warriors to protect if they haven't gotten themselves killed already, so the direct approach is the most likely to keep everyone alive.

Once you've secured the area, you can either enter via the front doors, or through one of the doors in the two towers in front. They both lead to the same general area, but you can avoid most of the enemies via the tower entrances. The careless and dangerous Aronil is the slowest of the companions, and it is fairly easy to leave him outside the Keep when you reach it, and just bring the other two, if they made it that far. It's all a matter of door timing when those two are close enough but Aronil is not. The same trick can be used to proceed with just Hjrondir, since he is the fastest of the three.

From the main room here, you can go to the stairs at the back of the hall to reach the Upper Chambers. Inside is a corpse carrying a key which helps to gain access to the lower areas (it's not required if you can open a 50 point lock on your own). Or if you want to avoid fighting and don't need the key, enter through the towers and just go down the stairs as low as you can go, avoiding the hallway that leads to the main room. The stairs to the Great Hall are at the bottom.

The Great Hall is just like it says, a very large, open rectangular room with lots of saber-wielding skeletons. There's nothing of real value here, but it's pretty hard to avoid having to fight every single skeleton to get to the other side and to the doors to the Guard Quarters. This area is very dark, so if you do not have a light source (carried or magical), you'll need to bring torches from the previous area; fortunately, they are plentiful.

The Guard Quarters are something of a rest from the fighting (not entirely, of course, but there are only five skeletons here, compared to the nine and 15 in the two previous areas). One thing not to miss is just before the stairs leading to the next section, turn around to your right and examine the wall behind where you came in. You'll find a secret door and a passageway that leads to a room with a bunch of loot, mostly Imperial arms and armor, plus some potions, ingredients, loose coins, and several sacks of gold. The door to the next section, the Dungeon, is  , though you can use the key if you got it before from the Upper Chambers.

Once you enter the Dungeon, the first thing you'll see is, at last, a break from all the skeletons. Instead, you'll be fighting rats. Not very difficult, except that there's over 30 of them, and all carrying the common disease Witbane. Unless you're a disease-resistant race, or you've already been cured of Corprus, you most likely will catch it. Make sure you've got a means to cure yourself, and you should probably wait until you've killed them all, or you may just get re-infected. This room appears straightforward, but instead of going straight through, look at the prison cell to the right of the stairs downward. You'll find a second secret entrance to the next section which gives you access to some more help.

The Caves
Either door from the Dungeon will lead to the Mine. If you took the secret door, you'll be in a passage with lots of Violet Coprinus and Luminous Russula. At the end, you'll find a reinforcement – a Khajiit archer named J'Hanir, an Imperial Legionnaire who survived the undead invasion and has been hiding out down here. Like Mara, he has a sword instead of a bow and arrows. A short drop from this section will lead to the main part of the Mine, which is where you'd have ended up if you took the other door. It is safer to go back around the long way; the companions may take damage from the fall even if you don't. There are some Raw Ebony veins here (plus some loose pieces), and more below, so if you've got the strength to carry it out, feel free to load up. You can also come back for it later, if you make the not terribly long trip over the water back to Firemoth, which is best done with Water Walk, Swift Swim, or Levitate; there will be no additional ship passage here.

Past the Mine are the Upper Caverns – a pretty much linear path leading down to the next section. Three skeletons here, and a whole pile of Raw Ebony. Not much else, besides miners' corpses.

The Lower Caverns are next. More ebony, more mushrooms, more skeletons. This is another linear dungeon crawl leading to the final section. In the water here, you'll find the door to the secret sea entrance from the outside of the fort. 

The Tomb
The last area of this place is a tomb in the Velothi style, swarming with skeletons, all led by Grurn, a powerful lich. His primary attack is a wicked area-effect Shock Damage spell, and he regenerates Magicka so fast that he can keep it up forever unless you damage his Intelligence enough to push his maximum magicka below the spell cost. His health also regenerates, so you need to kill him quickly or he'll just heal up again. A fast weapon helps here, to interrupt his spellcasting attempts. If any of your companions have managed to make it this far, this is where they will almost certainly die. His spell does 100 points of damage over 5 feet, enough to kill all but Hjrondir (due to his natural Nord resistance to shock) in just 2 hits, and Hjrondir will probably get himself killed fighting the skeletons if he hasn't already. In addition, Grurn has a shield which gives him a constant effect Luck boost (the very shield you came down here to get), which will make him somewhat hard to hit. The only hope for any surviving companions is to run as fast as possible behind Grurn, drawing his fire toward the rear of the space and dealing with him one-on-one, while the others beat it out with the skeletons without the lich raining lightning on them.

If you've been really struggling with this quest before dealing with Grurn, you may want to go back to the mainland, and train up and gain several levels, then return for the lich fight.  You can use various tricks outlined already to leave any still-alive companions here, though they may not remain in follower mode upon  your return, especially if you are away for 72 game hours or longer.

Once you kill Grurn, claim your prize: the Ward of Akavir, which provides Constant Effect Fortify Luck 25 points. Return to the ship and dialogue with the captain, Silm-Dar, to get back to Seyda Neen, or swim back to the mainland. If you don't like the shield, you can deliver it to Sellus Gravius for a 3,000 gold reward and 2 points of Reputation. Or you could sell it to somebody else for more money - its base value is 5,000. Otherwise, just keep it; nobody will care. Gravius will equip the shield, so if you want it back later, you'll have to fight him for it. Another option is to hit him with a long series of Disintegrate Armor and Calm Humanoid until it breaks, he unequips it, and you can pickpocket it from him.

Notes
If you have the Area Effect Arrows plugin, its Dread Firestorm Arrows will allow you to take out the skeletons very easily, often at extreme ranges or around corners.
Due to the sheer number of rats in the Dungeon area, it's possible to use them to raise any armor skill (or Unarmored) and Block very rapidly if you do not retaliate. You will need a supply of Restore Health potions (or equivalent) to keep up with the damage, some armorer's tools to repair your broken equipment, and a means of Cure Common Disease afterwards if you get infected with Witbane. Training-by-rats is best done at the entrance, so you can make use of that door in an emergency and to do repairs; if totally surrounded by rats you might not be able to escape easily. If you plan to train Heavy Armor this way, Fort Firemoth itself provides a large stockpile of the stuff, so you can use multiple suits if you forgot your armorer's hammer. Or switch between armor types you're carrying (or use a mixture of types) to train more than one. You can also rat-train Hand-to-hand – you can punch many rats and won't kill them while they raise your defensive skills. If you want to complete the quest and come back later to practice against the rats, try a wide area-of-effect Calm Creature to pacify them temporarily. Or remove their corpses on your way out so they respawn quickly.
With the companions in tow, you are very likely to need to use the Console command   ( ) in the Keep one or more times. Imperial architecture is not very follower-friendly, and there are several places where the companions can box you in with no other convenient means to get past them and continue. Other options include teleporting off the island and returning to it, or casting a Demoralize Humanoid on them to get them to run around for a while and get out of your way. Armed with this forewarning, you can also cast Mark in an open area in the keep in case you get stuck this way.
If you manage to keep any or all of your original followers alive and return to the ship with them, they will return with you to the mainland and stay on the ship. J'Hanir is different: If you've picked him up as a follower, he will be one until killed. He cannot, however, take the ship back to the mainland with you; you can return to Firemoth manually across the water (e.g. for more of the piles of heavy Imperial Steel Armor and Raw Ebony loot here), and then you can bring him home with you the way you came. If you killed Grurn before finding J'Hanir, this NPC will never enter follower mode, and he'll simply stay in his mine cave indefinitely.
The ship, along with the captain and any of the surviving original three followers, will disappear from the game after you turn over the Ward of Akavir to Sellus Gravius. J'Hanir does not vanish in this manner.

Bugs
 

Quest Stages
  
Note: Because this plugin was created before the Tribunal expansion was released (though it has a feature of the latter, namely the Lich as a new creature), it does not have "Quest Name" or "Finish" flags set up, and thus the quest does not show up as an active quest in your Journal, and it never officially "finishes" either.