The Elder Scrolls IV: Oblivion Guide - Daedric Shrine Quests
Location: Southwest of Cheydinhal, near Lake Popped.
Requires: Black Soul Gem
Level Requirement: Level 5
Reward: Skull of Corruption
To find Vaermina's Shrine, travel southwest from Cheydinhal. If you look at the map of Cyrodiil, Vaermina's Shrine sits right next to the 'P' in the 'Lake Poppad' text. When you reach the shrine, speak to Aymar Dovar there. He tells you that a Black Soul Gem is needed to summon Vaermina. Your character must be at least level 5 to begin this quest.
Offer a Black Soul Gem at the Shrine of Vaermina to summon the Daedric Lord.
Getting your hands on a Black Soul Gem is no easy task. First, you'll need to find a plain, empty Grand Soul Gem. You also need some way to cast a Soul Trap spell. You should be able to purchase an empty Grand Soul Gem from the Mystic Emporium in the Imperial City Market District. If the proprietor doesn't have a Grand Soul Gem in stock, use the wait feature to pass a day or two and check back in.
The Soul Trap spell can be purchased from several of the Mages Guild halls in Cyrodiil. If you want direction, travel to Cheydinhal, locate the Mages Guild there, speak to Trayvond the Redguard while he is selling spells, and buy the Soul Trap spell from him.
When you have an empty Grand Soul Gem and a Soul Trap spell, you'll then need to find a Necromancer Altar where Black Soul Gems are created. Dark Fissure, which is just east of Vaermina's Shrine (across the Reed River), is one such altar. It is near the tip of the Reed River on the eastern side. The Altar is in front of the cave entrance.
Place an empty Grand Soul Gem in the Altar in front of Dark Fissure Cave. Then, hit the Altar with a Soul Trap spell while light is shining upon it.
To create a Black Soul Gem, place the empty Grand Soul Gem in the Altar, and cast the Soul Trap spell on it. This will only work when light is shining on the altar, which happens rarely. If light isn't shining on the altar when you first arrive, use the wait feature to pass 24 hours. If light still isn't shining on the altar, pass another 24 hours. Continue this as many times as necessary. So, while light is shining on the altar, put the empty Grand Soul Gem inside and hit the altar with your Soul Trap spell. Afterwards, open the altar and retrieve the Black Soul Gem. You may also catch a Necromancer there, and in that case, you can just steal the Black Soul Gem from the altar when you see him cast Soul Trap. Once you have the Black Soul Gem, return to Vaermina's Shrine and offer it to the altar to converse with her.
Vaermina wants you to retrieve an orb that was stolen by a wizard named Arkved. You must travel to his tower, retrieve the Orb of Vaermina, and bring it back to the shrine. Arkved's tower is south of Vaermina's Shrine. With 'Vaermina' set as your active quest, follow the marker on your compass to reach the tower. Find the entrance and head inside.
You'll meet some resistance along the way, so be careful. Follow the marker on your compass through the initial area and enter Arkved's Void. Cross the series of bridges here and enter Arkved's Lost Halls. You will encounter several Daedra in these halls, so remain vigilant. Follow the arrow to the door to Arkved's Hall of Changes.
There are more Daedra in this area. There are also magic crystals that will sap your health, so avoid staying in a room with one for too long. Continue following the arrow on your compass to reach a Trap Door to Arkved's Rending Halls. In the Rending Halls, you'll find—you guessed it—more Daedra. The last area is Arkved's Death Quarters, where the Orb of Vaermina can be found. Enter the Death Quarters and retrieve the Orb of Vaermina, which is sitting on a table in the corner of the room.
Retrieve the Orb of Vaermina from Arkved's Death Quarters.
Once you have obtained the Orb of Vaermina, head through the wooden door that leads back out to the Nibenay Basin and return to Vaermina's Shrine. Summon Vaermina once more; she will reward you with the Skull of Corruption for completing the task. This interesting staff will clone its target. Have fun!