Transferred from forum posting June 30^th, 2016. Edits suggested on original thread, but unclear if these are being incorporated (or need to be).
http://www.tamriel-rebuilt.org/forum/mages-guild-ghost-gem
 

Short summary: This is a mid level quest for the Mages’ Guild of Old Ebonheart. The player is sent to rescue a missing Guild member only to find them already dead, their soul trapped inside a necromancer's soul gem. The player has to decide what to do with the distraught soul with three possible outcomes.

Long summary: Valkreia Krex, a quest giver in the Mages' Guild of Old Ebonheart, tasks the player with finding Missa Rhyle, an apprentice Guild member. Missa Rhyle was sent to explore the cavern of Ghand [to be created] where supposedly a collection of soul gems of a late necromancer was waiting to be retrieved. Missa Rhyle hasn't been heard of in a while and Valkreia Krex is starting to worry about her. Player is to find Rhyle and bring her back to the guildhall. Valkreia Krex gives the player directions to the cavern. She tells the player to be careful: though the Guild had assumed that the necromancer's lair was uninhabited – which why they sent a rookie to explore it in the first place – they are now suspecting they were direly wrong.

Indeed, the necromancer, Vohur, is still very much alive and is confronted by the player soon after they enter the cavern. Vohur will taunt the player and tell them that they'll soon share Missa Rhyle's fate – an eternity in Vohur's captivity. The player fights and defeats Vohur and a number of his undead minions. After the battle the player hears a voice crying for help: it's Missa Rhyle, communicating telepathically with the player. She tells the player that she only narrowly escaped Vohur's minions. She says she's now trapped in a dark room, in the farthest corner of the cavern, and is afraid to come out. With a key found on Vohur the player can now explore the rest of the cavern. There are a few undead minions left to resist the player as they search for Missa Rhyle. As they are reaching a final locked door Missa Rhyle says they can feel the player's footsteps. She must be behind that door. The player opens the door and enters the room. There are skeletal remains here and there, signs of a struggle perhaps, but no one alive in sight. Missa Rhyle calls the player again, asking where they are. The player will tell Missa that they are in the room she said she was in. Missa says she can't see the player and asks them to light the torches. The player will tell her that the torches are already lit – have been the whole time. Missa becomes somewhat distraught and says she doesn't understand. The player will explore the room. On a crude altar there is a dagger and some necromantic tome. Behind the altar there lies a dead body, that of Missa Rhyle. She has been killed. Near the body is a soul gem. The player now has an uneasy conversation with Missa Rhyle. She is dead, her consciousness has been trapped in the soul gem and she doesn't know it – yet. At first she dismisses the news, but as she slowly starts to remember that she indeed did die she becomes increasingly horrified and repetitive, losing her sense of self (e.g. I can't see, I can't see, y'know, like an uncanny broken vinyl record). The player's conversation ends as Missa Rhyle loses her focus and seemingly fades away. The player will take the soul gem and return to Old Ebonheart.

Valkreia Krex is revolted to hear of Missa Rhyle's fate. She says that in her opinion trapping a human's soul inside a soul gem is a crime worse than murder and being trapped is a fate worse than death. Her first instinct is to smash the gem into pieces to free Missa's soul, but she says that the player should consult with Zissicheeiva, the Guild's enchanter, before making up their mind. Valkreia also mentions Hastophos Venifer, the friendly neighborhood necromancer in Old Ebonheart, who might be provide some insight. [Option 1] The player breaks the soul gem. The soul gem is destroyed and Valkreia is somewhat content of this outcome. The player gets some relatively generic reward, perhaps gold and a new spell.

If the player talks to Zissicheeiva she'll strongly disagree with Valkreia's proposition. She says that breaking the soul gem would only cause what remains of Missa Rhyle's soul to become fragmented. Fragmented and unusable. Zissicheeiva has a different idea. She asks the player to give her the soul gem. She says she will use it to enchant a weapon for the player. Zissicheeiva says that Missa is already dead, beyond help, but binding the magick of her soul into something useful and beautiful would mean she didn't die in vain – ”it is what she would have wanted”. [Option 2] The player gives the soul gem to Zissicheeiva. The player returns later back to Zissicheeiva to receive an enchanted silver weapon, macabrely named Missa Rhyle. Player gets a major disposition bonus for Zissicheeiva, but Valkreia (and Hastophos if the player talked to him about the situation) will have their dispositions lowered. Could be that at first the weapon will from time to time sob to itself or ask ”can anybody hear me?”, but in the end it will cease doing so.

If the player pays Hastophos Venifer a visit a third, a bit more complicated, path becomes available. Hastophos Venifer, a necromancer himself, will denounce Vohur's actions. However, he finds both Valkreia's idea of smashing the soul gem and Zissicheeiva's idea of using it for enchanting equally barbaric. Like Zissicheeiva he says that smashing the soul gem would irreversibly break Missa's soul. On the other hand using the soul for an enchantment is like condemning Missa into an eternity of forced labor. She'd slowly lose her own identity and turn into the object she was bound to, according to Venifer. He also reveals that he suspects that though Missa Rhyle hasn't communicated directly with the player since they left Ghand she's likely able to read the energies around her; that is, she's to some extent aware of what is going on. Venifer hopes that the player and the Guild members have been discreet and have not unnecessarily upset her with their discussions. Venifer says that it's difficult, though not impossible, to free a soul from within the soul gem. He asks the player to leave the soul gem to him and find and come back with the following items: an empty sheet of paper, a quill, an inkwell, a moonmoth wing, and black rose petals. [Option 3] Player helps Venifer summon Missa's soul from within the soul gem. Old Ebonheart has all kinds of shops so the items Venifer asked for should not be hard to find. The player returns and finds Venifer in his study. He tells the player to hold on to the quill, the inkwell and the paper as the ghost of Missa might want them to write down a message. He takes the moonmoth wing and the black rose petals from the player and performs a ritual mumbling a few words. There's a burst of light and the spectral apparition of Missa Rhyle emerges for a moment for a final talk with the player. She is confused and distant, but depending on the player's previous actions (as in what they said to other NPCs concerning Missa's situation) she'll be either a mixture of sad and grateful or sad and bitter. Before moving on to what is supposedly Aetherius, Missa will have the player write down her last goodbye which she asks to be delivered to her family in Cyrodiil. After that she will permanently fade away, leaving the soul gem empty and broken. Venifer will congratulate the player on a job well done. Valkreia will be pleased with this outcome, promising to make sure Missa's letter gets delivered. She will teach a unique spell to the player. Zissicheeiva will lower her disposition towards the player mocking them for being a ”necromancer's apprentice”.

None of the three different choices is meant to feel like the “good” or “right” ending.