The Black Star (quest)

Walkthrough
To initiate the quest, ask about rumours from Hulda in Whiterun then make your way to the Shrine of Azura. Once there, speak with the priestess, Aranea Ienith.

Find the elven mage from Aranea's vision
The elven mage from Aranea's vision is Nelacar who is staying at the The Frozen Hearth in Winterhold.

Speak to Nelacar
Speaking with him reveals that there exists a soul gem which can be reused: Azura's Star. However, that soul gem was lost along with the mad mage who was experimenting with it, Malyn Varen, when he fled with a few loyal students to Ilinalta's Deep.

Find Azura's Star
Proceed to Ilinalta's Deep, which is located along the north shore of Lake Ilinalta, north of Falkreath.

Note: (Possible bug) Inside, the pathway from the first area to the second (Ilinalta's Deluge) may be blocked by a large boulder, save and reload (or exit the dungeon and reenter).

Find the Broken Azura's Star, all the while keeping an eye out for soul gems.

Tell Azura / Nelacar you are ready to enter the Star
To restore Azura's Star, the Dragonborn must choose between the following options:


 * 1) Returning the Broken Azura's Star to Aranea Ienith, which will ultimately lead to a reward of Azura's Star.
 * 2) Returning the Broken Azura's Star to Nelacar, which will ultimately lead to a reward of The Black Star.

Destroy Malyn Varen's soul
Malyn Varen's soul is trapped inside the broken star and the Dragonborn must enter it to kill him. Three quite tenacious Dremora Vakynaz (contain Daedra Hearts) will try to protect the mage though. This is done with the help of either Nelacar or Azura herself.

The Dragonborn then either receives Azura's Star from Azura or The Black Star from Nelacar.

Note: Supporting Azura will turn Aranea Ienith into a possible follower.