The Imperial Library

In the missing prince quest, you have learned that late King Lysandus' mistress, Medora Direnni, might help you in your mission. It is also known that she lives on the isle of Balfiera, in a tower.

On the map of Balfiera, there's only one structure that could qualify as a tower. And it happens to be called "Direnni Tower". Talk about straightforward.

This whole quest seems to be somewhat more action-oriented than knowledge-oriented, so you're not going to learn much outside of obvious from the in-game dialog. Instead, allow me to put things in a perspective for ya.

As the PGE states: Isle of Balfiera

This island in the Iliac Bay has been used for centuries as a neutral meeting place for diplomatic negotiations and treaty signings by the kingdoms of High Rock. It is also famous for the enigmatic structure known as Direnni Tower, a circular tower soaring hundreds of feet into the sky. The traditional ruler of the island is known as the Castellan of Balfiera, perhaps reflecting his original role as commander of Direnni (or Balfiera) Tower, which was used as a fortress, prison, and palace by the infamous Direnni Hegemony. Even more curiously, the hereditary Castellans are High Elves, the only known Elven ruling family remaining in human lands. The Castellans continue to reside in the Tower, although its true provenance and purpose remains a mystery. A recent archaelogical study, using the latest techniques of divination and sorcery, has pushed the Tower's construction date back to around ME2500, making it by far the oldest known structure in Tamriel. Although it has been much modified and added on to over the years, its core is a smooth cylinder of shining metal; the Tower is believed to extend at least as far beneath the surface as is now visible above, although its deepest bowels have never been systematically explored.

Obviously, Medora Direnni is the last Castellan. This also means she's a High Elf by ethnicity; Tedders specifically confirmed the other day that she was meant to be one in TES2: Daggerfall. Needless to say, during the conversation her face looks nowhere like that of a High Elf woman.

History aside, after a long and tedious battle you reach the deepest bowels of the Tower, where a fine-looking young lady happens to live, surrounded by Ancient Vampires, werewolves, lesser Daedra and other cute, cuddly creatures. As you soon learn, she did not choose this residence willingly; instead, she is trapped there. She wants you to pay a visit to Nulfaga, mother of King Lysandus, and fetch a rare ingredient, the horn of a Great Unicorn. The horn is what Medora needs to break the curse on Direnni Tower.

Just as Medora warned, Nulfaga is obviously a clinical case. The wheel is still spinning, but the squirrel is long dead, if you know what I mean. In my own experience, all you can get from Nulfaga is mad ravings. For the sake of demonstrating once again how good the Bethesda boys were at composing rabid rants, I'll quote Nulfaga here:

United thoughts and counsels, equal hope
And hazard in the once glorious enterprise
Joined with me once, now misery hath joined
In equal ruin! Eternal, eternal, eternal ruin.
Oh, my child, why wouldst thou not listen, thy ear, thy glorious mortal face, thy throat, and the arrow. Oh misery.
Choosing out few words most horrible,
Let none them read! Verses, verses frame which with and other spells like terrible curses
Heaven! Curse Oblivion! My boy! My boy is dead and let Tamriel tremble until he and I findeth peace denied.
Say, what strange motive,
Goddess! could compel an arrow to my beloved Lysandus' bare throat? Did he die there mourned and blessed or are my pretty birdies all turned to graywings? I search the afterworld, the underworld, and the world-between and no where do I find the lightness of my son. Oh, madness to thy breast I cling suckling!
We are only like dead walls or vaulted graves, that, ruined, yield no echo. Oh, this gloomy world, in what a shadow or deep pit of darkness doth, womanish and fearful, mankind live. How came Lysandus by his death? In a mist, I know not how. Oblivion not come yet? I'll it nearer by a perspective, or make a glass that shall set all the world on fire upon an instant. I cannot sleep; my pillow is stuffed with a litter of porcupines.

There's a common theme to these, by the way - arrow in the throat. Make a mental note.

After hearing something like that, only a very naíve adventurer would hope for Nulfaga's cooperation. Another happy dungeon romp, this time through Shedungent. The Horn is stashed away in some far-off room. Who would treat a rare, obviously expensive item like that?

Matter of fact, I have found a hint that Nulfaga might actually give you the horn under certain circumstances. Among other answers, there's the following one: Of course I will give Medora the horn of the Great Unicorn. She was a favorite of my beloved Lysandus after all.

I personally never saw her say that. Maybe if you have an exorbitant reputation with her... All in all, this kind of response is even more unlikely considering what Medora says when you bring her the horn:

You have succeeded in a most dangerous enterprise, Qwerty, but many more such trials await you. By bringing the horn to me, you have helped me lift the curse the Queen Dowager placed on my tower. I hope I can count on you for further aid. For now, take this (magic item) as your reward.

See, Nulfaga was the one who cursed Direnni Tower in the first place. Some kind of Freudistic mother/lover jealousy, I guess. Or maybe she just went off the bonkers, like plentiful evidence suggests.

Medora politely dismissed you this time, but her part is not over yet. When she needs you again, she'll contact you...