Skyrim:Repairing the Phial

Quick Walkthrough
Note: This quest can only be started after gaining full access to the Throat of the World during the quest of the same name. 
# Talk to Quintus Navale about repairing the White Phial.
# Find the items required.
# Return to Quintus Navale.

Detailed Walkthrough
One Last Attempt
thumb|right|Skyrim:Nurelion|Nurelion on his deathbed 
A few days after the failed attempt to help the alchemist Nurelion realize his life's ambition (so long as you have unlocked the top of the Throat of the World by completing the similarly named quest), a courier will seek you out with a letter from Quintus Navale (Nurelion's assistant) who has grave news, and seeks your help. 

Head to Windhelm and locate The White Phial in the market district. In there, Nurelion will still be in his bed, coughing and slowly dying. Quintus, however, will be more than ready to explain what is needed to repair the Phial: "I have some thoughts. There are three crucial elements. Some may be easier to find than others. On the top of the Throat of the World is a patch of Unmelting Snow. No heat can touch it. Then we need the tusk of a mammoth, ground to a fine powder as only the giants know how. The final step is tricky. It requires the briar heart from a Forsworn of the Reach. If you can bring me these materials, the Phial can again be made whole."

Gathering the Items
Although he claims not to be as skilled as his master, Quintus will provide quite a bit of information on each of the items to explain why they are needed for his plan to repair the Phial: 


thumb|right|Repairing the Phial
thumb|right|"Master, look. It's the Phial."
The rather unremarkable patch of Unmelting Snow can be found at the Throat of The World. Mammoth Tusk Powder is in a large vat beside the giants at Stonehill Bluff, and it is possible to pick up the powder without aggravating the giants. Note that the Mammoth Tusk Powder is different from the alchemy ingredient Powdered Mammoth Tusk. A Briar Heart can be acquired from a dead Forsworn Briarheart and can be obtained from multiple Forsworn camps; one will be marked on your map. 

Repairing the Phial
When you return to Quintus with the three items, he will be relieved: "Thank the gods. I'll get to work on the Phial straight away." He will then leave his spot behind the counter and get to work at the alchemy lab in the corner. Once he is finished repairing the Phial, he will head upstairs, eager to show his master what he has accomplished: 

Quintus: "Master, look. It's the Phial." 
Nurelion: "What? How?" 
Quintus: "It doesn't matter. Look, it's refilling with your tonic as we speak." 
Nurelion: "Marvelous."

Nurelion will then die peacefully and Quintus will turn around and express his gratitude: "He is gone. But thanks to you, he died knowing his life's work was not in vain." When you say you are sorry to hear that old Nurelion is dead, he will respond: "As am I. You acted very nobly in helping my master realize his life's work. Thank you for that. As for myself, I've always been content to simply be an alchemist. I fear keeping the Phial would just remind me of Nurelion's obsession, and how it consumed him. Here, keep it. You are as much a part of its legend now as Curalmil was. I hope it brings you the happiness that my master desired."''

The Reward
You have a number of options for which kind of liquid the Phial will be able to regenerate: 
I'd like it to have the power of healing. (restore health for 100 points)
I want to resist the forces of magic. (20% resist magic for 60 seconds)
I want to be tougher in battle. (+20 stamina for 300 seconds)
I want to strengthen my magical skills. (+20 magicka for 300 seconds)
I want to deal more damage in battle. (+50% to one-handed damage for 60 seconds)
I want to be better hidden in the shadows. (20% harder to detect for 60 seconds)

You will be given The White Phial, which functions as a potion of the nature you chose. Drinking it moves it to the Miscellaneous section of your items menu as The White Phial (Empty). It refills after 24 hours. Attempting to use the empty phial duplicates it, but only one phial will fill after the time has passed.

Notes
Nurelion's dead body will disappear after some time. You can find his remains inside the coffin in the Hall of the Dead.
After Nurelion is dead, many of the contents of his store will be free for the taking, including many useful ingredients.
If you are on an assignment for the Thieves Guild involving The White Phial (the shop), complete it and turn it in prior to completing this quest. Nurelion's passing at the end of the quest, though not caused by you, will still trigger you to fail the job for "killing".
It is possible to reach the peak of the Throat of the World early, by using a horse to climb the mountain; however, doing so will not let you start this quest early - you have to advance the main questline in order to get the letter from Quintus Navale.
Oddly enough, you cannot use a Briar Heart (item) that you found earlier - or, indeed, one that you buy from an alchemist's shop (including from Quintus himself, now that he has taken over the shop from Nurelion), or find lying around somewhere: you will have to go and kill an actual Forsworn Briarheart AFTER starting this quest, to get one that Quintus will count.

Bugs
 
This bug is likely to occur if you have killed the Forsworn leader of Red Eagle Redoubt before(probably during  find Red Eagle's sword). If so, use the following console commands:   and   to resurrect him. Wait a few real-world minutes then fast travel to any major city and the courier should show up. If the courier still fails to appear, try the command  .
 
You may be able to find the courier by using the console command   to move yourself to him.
  Note that this recurrs in Skyrim Special Edition, and appears not to be fixed by the Unofficial Skyrim Special Edition Patch (4.1.0)
Keep the briar heart in your inventory, collect the other two ingredients and use the console command:  .
 
 
 
 If you don't want to install the unofficial patch, you can manually reset all of the items' quest item status through the console command   , followed by  . 
 
Use the   console command to advance the quest.
 
This may happen because the Mammoth Tusk Powder was not marked as a quest item, allowing you to drop or store it before you brought it to Quintus. If you stored it, retrieve it and talk to Quintus again.
 If you can't retrieve it, you can manually spawn it by using the console command  .
 
 
 
You can avoid this happening by removing his essential status before Quintus shows him the Phial. Open the console and type in  .

Quest Stages