Online:A Mortal's Touch

Quick Walkthrough
# Read the ''Dread Lady's Letter''.
# Find Lyranth in the Shrine of the Black Maw/Shael Ruins/Erokii Ruins.
# Investigate the Imperial Cache Annex.
# Enter Ne Salas and talk to Eveli Sharp-Arrow.
# Explore the Ne Salas Cache Annex.
# Talk to Eveli's contact outside Elden Root.

Detailed Walkthrough
You can either accept the quest from the Crown Store or speak to Rogatus Cinna, who is located at all three of the following locations: 
 

In either case, you will receive a letter from a Dremora named Lyranth. She's opposing the forces of Mehrunes Dagon, and requests your aid. The fate of the world hangs in the balance. When you open the letter, a location is marked on your map. If you accepted the quest from Rogatus Cinna, you'll find that there's a cart right next to him which will take you to this marked location, which will be just outside the relevant delve. This location will depend on which alliance your character is from: in the Aldmeri Dominion it will be the Shael Ruins in  southern Malabal Tor; while in the Ebonheart Pact it is the Shrine of the Black Maw, located in northwestern Shadowfen. The location within the Daggerfall Covenant is Erokii Ruins in northwestern Rivenspire.

If you choose to not use the cart, you can instead find your own way to the area by Wayshrine or Caravan and make your way to the delve. Once inside the delve, you will need to make your way to the marked location on the map. 
 

When you reach the location, you will find Lyranth in front of a purple force field, choking out a Waking Flame Cultist, interrogating him on what interest his cult could possibly have in this ruin. He provides no useful information before he is accidently killed by Lyranth. Speak with the Dremora to see why she called for you. She's been tracking the cult of the Waking Flame for a while now. Lyranth informs you that there is an Imperial cache behind the nearby ward, and she can't pass through it; she needs a mortal to deactivate it. You are handed   and she instructs you to use it to bring down the ward. It works. Activate the bookshelf to enter the Imperial Cache Annex.

Lyranth senses that there are more wards ahead, and sends you to investigate. Head down the stairs to the south. There are three wards with caches hidden behind them. Deactivate the wards and search them. You'll find a   in the western cache,   in the eastern cache, and the   in the southern cache. When you've recovered all three items, speak with Lyranth back in the entrance to the north.

The scroll you found is enchanted so it can't be opened or read, and the schematics are for a vault of Daedric design which is protected by a complex arcane matrix. The map points to Ne Salas, an Ayleid ruin in Grahtwood. Lyranth opens a portal to a location near the ruin so you can investigate it while she reads the scroll. The portal deposits you just down the hill from Ne Salas. Head east up the slope and enter the ruins.

When you arrive, you'll find Eveli Sharp-Arrow and two Wood Elf Scouts, all with their bows drawn. Speak with Eveli, who lowers her bow when she notices you're not dressed like one of the cultists. Talk to Eveli. She's also here to find the Imperial caches you're after, and explains that she found these Dominion soldiers under siege by the Daggerfall Covenant and the Dagonites. The cult's leader, Doombringer Eshil, paid off the soldiers so the cult could pass through unmolested. Eveli reports that Eshil is being followed by a scholar. She asks you to clear a path so she can catch up to you after she leads the Bosmer scouts to safety.

Head east through the ruins until you end up at the northwestern end of the runs. Turn south, and head east through the southern hallway until you reach the middle of the hall. You'll find the Imperial cache in a nook breaking off south in the middle of the southern hallway. You'll find two dead Wood Elf Laborers in front of the bookshelf leading into the annex, as well as an injured scout named Merthin. He tells you the cultists destroyed the ward and entered the annex. If you speak to him, he informs you that Eveli healed him up before going after the cultists. You should follow suit.

Enter the Ne Salas Cache Annex and talk to Eveli. Doombringer Eshil and his companion, Pedagogue Eralin, are down below. The Pedagogue is attempting to dispel the ward on a cache. Doombringer Eshil teleports away while the scholar works. Eveli suggests you split up and try to make it down there before she opens the cache. While you're making your way downstairs, the scholar will tell one Disastrix Maglagor to keep you at bay. Kill him and proceed. Eveli shoots the Pedagogue dead with an arrow before she can manage to dispel the ward. 

Now's your chance to loot the chest for Lyranth. Your attempt to open the cache fails, but Eveli decides to try it herself. It works. As soon as the ward goes down, Lyranth appears. She tells you to loot the cache. There was an   and a   inside the chest. Talk to Eveli when you have the items, then talk to Lyranth. 

Lyranth opens a portal at the crossroads south of Elden Root's Mastercraft Mediator and Undaunted Enclave. Here, you'll meet Eveli's contact: her brother, Beragon. He was an adventurer before he became a scribe for Emperor Moricar and his son, Leovic. He knows Leovic's code very well. He interprets the document and produces a translated copy for you to read. Take the  , then talk to Eveli to finish the quest.

Notes
The quest was made available on March 31, 2021. It was previously playable in Patch 6.3.5 by Pact players who read the letter at the Shrine of the Black Maw, but was fixed in 6.3.6.
 

Quest Stages