Online:The Blood of Nirn

Quick Walkthrough
#Enter the Skyreach Hold.
#Explore Skyreach Hold.
#Defeat Exarch Arnoth.
#Return to Nendirume in Dragonstar.

Detailed Walkthrough
Speak to Nendirume
Travel to the Skyreach Wayshrine and head towards Skyreach Hold in the east. Near the bridge you will see Nendirume who warns you not to go farther as the Scaled Court has taken hold of the ruins, searching for more nirncrux. She then asks if you could help her and investigate what the cultists are up to.

Explore Skyreach Hold
Cross the bridge and enter the hold. You will have to fight through a few groups of Scaled Court cultists. Continue south until you come to a large room where you will witness a conversation between the hologram of Exarch Arnoch and Nathrasa Shimmerscale, one of the Scaled Court assassins. Exarch Arnoth confirms that they have found a great source of nirncrux somewhere inside the hold. Your arrival, however, interrupts their conversation, so Nathrasa proceeds to deal with you. You will have to fight her and a couple of Scaled Court cultists assisting her. Notice that while there are two Scaled Court Battlemages accompanying Nathrasa, they won't attack unless you go too close, thus it is possible to fight them separately.

When you head eastwards to the next room, you will be met by more Scaled Court cultists and a mantikora. Head towards the southern exit of the area. You've now come to Skyreach Pass, which is a wide bridge leading to the next part of Skyreach Hold. On the bridge you will have to fight yourself through a gauntlet-type encounter with numerous Scaled Cultists and a couple of mantikoras.

The next area has more groups of Scaled Court cultists accompanied by occasional Iron Orcs. You will soon thereafter face an encounter with Navren Daral, a Dunmer Scaled Court member and Akkra gra-Korma, an Iron Orc shaman. This is a rather straightforward fight, but beware of the strong Uppercut attack of Navren Daral, especially if you are solo.

You have now arrived to a cave where you will meet several Iron Orcs and their trolls. Taskmaster Zagrakh can be found here as he is overseeing the work in the caves. After you kill Zagrakh and the nearby trolls, the final boss of this encounter, Rakmath the Breaker, will appear. As a troll, he uses the powerful stone throw attack which is essential to avoid.

Exit the cave through a waterfall which leads you to an open area - in fact, you are now under the Skyreach Pass bridge where you had the gauntlet encounter. Here you will find a powerful wamasu, Azdarmu the Awakened. Defeat Azdarmu and continue forward to the last area.

Being inside the hold again, you need to kill a few more groups of Scaled Courtists, Iron Orcs and mantikoras until you meet Exarch Arnoth.

Deal with Exarch Arnoth
During the first phase, the Exarch is using two ranged spells which you need to be aware of - Impending Storm and Fire Runes. Both of them are clearly marked on the ground so you just need to move away from the targeted area as soon as possible. He summons Power Orbs throughout the fight which you will need to eliminate fast, but these have very little health so it's not difficult. 

At about 35% health he will stop using ranged attacks and start using melee attacks while following the aggro target closely. Having a speed buff coupled with a damage absorption shield or an ability like Shuffle will help you remarkably, as you will then be able to keep yourself out of range for him and even if he reaches you, the attacks will not kill you instantly. Every now and then he will attempt to teleport to you, but if you are ready with a dodge roll or have shielded yourself, you should be able to handle this without any problems.

When you have defeated Exarch Arnoth it is time to head back to Nendirume who is waiting for you in Dragonstar.

Notes
You can skip several, if not most of the bosses on the way, as they are not part of the quest objective.

Bugs
 

Quest Stages