To begin with the boring(?) stuff, some

Linguistic notes:

I believe the Ainur had a tongue of their own, but since only few words of that remain (such as Mahanaxar, Ring of Doom), I have chosen to use Quenya until speakers of other languages appear.
Some Quenyan names you will encounter in the first chapters:
Angamando: Angband
valarauko: balrog
Nurtahuinen: Thuringwethil
Moringotto, Morion: Morgoth

The name 'Fanian' is based on these four successive entries in the ecxellent Quenya Corpus Wordlist compiled by Terrence Donnelly:
'...fana the "veils" or "raiment" in which the Valar presented themselves to physical eyes, the bodies in which they were self-incarnated, usually in the shape of the bodies of Elves (and Men) (RGEO:74)
fána, fánë "white" (Markirya)
fanya "(white) cloud" (FS); pl. fanyar in Namárië (Nam, RGEO:67)
fanyarë "the skies" (not heaven or firmament - the upper airs and clouds). Note that despite its English gloss, fanyarë is a singular word and therefore takes a singular adjective/participle, as in fanyarë rúcina "ruined skies" in Markirya (see MC:220, note 8 for this translation)...'

The stem nurta- that I have used in both 'Nurtalessen' and 'Nurtahuinen' means hiding, that is, secret:
'...nurtalë "hiding" (evidently a verbal stem *nurta- "hide" with the verbal noun ending -lë); Nurtalë Valinóreva "the Hiding of Valinor" (Silm)...' [Quenya Corpus Wordlist]
As for Thuringwethil's Quenyan name, the origin is this word:
'...nuruhuinë "death-shadow" (LR:47, 56, SD:310)...' [ibid.]

And lastly, the entry that gives us Morgoth's Quenyan name:
'...morë "dark, darkness" (Letters:282); morimaitë "black-handed" (LotR3:VI ch. 6). Moriquendi "Dark Elves" (SA:mor, WJ:373). Moringotto "Black Foe", Sindarin Morgoth. The oldest form is said to have been Moriñgotho (MR:194). Morion "the dark one", a title of Morgoth (FS). Morifinwë "dark Finwë", masc. name; he was called Caranthir in Sindarin. Short Quenya name Moryo. (PM:353)...'

WOMAN OF SECRET SHADOW
by Arwen Imladviel

One: End of Innocence

Once we were many, now I alone remain. This is the book of my nights that I write in my seclusion during long days in my silent hall which sunlight never enters. For I am vampire, the vampire I suppose these days, the last of my kindred.

Why am I writing? It will become plain as the story proceeds that I am a creature of secrets. Why am I putting so many of them down in a book like this? Well, first of all, it is a rare creature indeed in this age that can see the meaning in these symbols and this forgotten tongue. If anyone ever will read this book, which I strongly doubt, her or him I greet: already you know much of the secrets of darkness, and the fact that you hold this book in your hands proves beyond doubt that you are truly a mighty one and in service of Melkor and those who are of Melkor. Such a one also am I, you and I and most likely none other in this world, this age. Therefore, read on.

There was a time, in the Spring of Arda, when I enjoyed the feeling of warm light on my wings. The light of Illuin and Ormal and nothing less, and the light of the oldest stars. I was a spirit of the air, a servant of Manwë. A faithful servant I was and as messenger swifter even than Eönwë. I wore white wings like a swan. I weep now to remember my innocence, yet if I lived those times again I would make the same choices.

Fanian! Your hair like billowing clouds full of golden light! Fanian, your raiment always white and shining bright. Fanian you were my joy, my love, you were my doom.

Fanian was a merry maiden, in power even lesser a Maia than I. Seldom have I met another who would so wholly surrender herself to the physical shape she had chosen to house her spirit in. She radiated joy and harmony. She rejoiced to possess beautiful flesh, and a pair of wings. She loved the caress of wind, the freshness of rain, even the excitement of thunder. Her wings were transparent like those of a dragonfly, so very fragile-looking and yet so strong. Her eyes were blue, her hair like golden thread. Slender she was and soft-featured. And I loved her more than anything else in all Eä.

In her visible shape - and she seldom abandoned it - Fanian made flesh the whole of her being. The Valar could never do such a thing; for their spirits are so immense that few could bear to behold their radiance. Some Maiar hide aspects of their spirit because of similar reasons - Arien of the Sun was much less bright and burning when she dwelt in Valinor. Had she been as she now is - oh, how I fear her merciless rays! - she would have burned the grass on which she walked. Some wish to conceal their true being for reasons of their own, many are too modest to show their power, while others take no shape at all, preferring the full freedom of a spirit.

As for myself, secrets are what I am made of. Those days I was called "the one with a hidden name", Nurtalessen. I was few-worded but known as a good listener, and I kept most carefully all the secrets I heard. We were each other's opposites, Fanian and I, and that was what kindled our love. I hungered for her open innocence; she was fascinated by my mysterious silence.

Yes, we were lovers. For Fanian it was simply impossible to show her love without physical expressions. We never thought that it was unusual for two women to love each other so, or if we did, we cherished our love all the more as a rare and special thing. Nor did we consider it as a loss of innocence, for how could two pure hearts joined together result in anything stained?

All that matters but little now. Ages past I chose a path of darkness - yet it was not I who destroyed Fanian.

This happened after Melkor broke the Lamps, when we lived in Aman, before the awakening of the Eldar. We were visiting Middle-Earth in its eternal twilight under the stars. I loved to listen to the secrets trees whispered to each other in the shadows, and the hidden movements of shy creatures. In starlit night everything wears veils of mist and darkness, and things unseen are the most beautiful of all. Fanian flew high above the trees and sang of everything that was in her heart: peace and love and wild joy. She shone in the darkness like a bright golden star.
Then I could hear her voice no longer, nor the sound of her wings. I spread mine and flew where I had last heard her; she was no longer there. I searched the ground, I called out her name as loud as I could. It seemed like forever until I found her, but a glance at the stars told me only hours had passed.

Fanian was huddled small under a leafless tree. She shivered, but not of cold. She was weeping. Her shape no longer shone with the heavenly radiance of joy.
'Are you hurt, my love?'
She did not answer. I wrapped my arms around her and held her. At first she stiffened, but relaxed as I softly whispered:
'I'm here. It's all right, I'm here.'
I stroked her hair until her breathing calmed. Soon she was asleep in my arms. I held vigil over her and wondered what had happened to her. Some kind of accident? Some monster in the forest?

When she woke her eyes popped suddenly open and she screamed: 'Let me go!'
I released my hold and she stood up. She stared at me and finally recognised me.
'Nurtalessen! I thought -'
'Please. What did you think?'

She told me.

Fanian had been snatched from the air by something bigger and stronger than her. It had covered her mouth and flown her far, and then landed in the forest. It had held her under its wings, something scaly covering her mouth. It had raped her, raped with a male member; so large it tore her flesh. Its semen burned her like fire, like molten iron. She struggled all she could and even tried to bite whatever ghastly limb held her, but she was helpless. She knew she could have left her physical body, but she guessed also that if she did it might be ravaged so badly she would never be able to take physical shape again. The creature satisfied its evil lust and released her - but when she stumbled away from it, it reached out suddenly with sharp claws and tore her gossamer wings. She turned to face the monster and saw it was man-shaped. It had wings of leather like a giant bat, but it also had feet and hands, and it stood upright. It wore clothes; a dark cloak and a horned iron helmet on its head. The scales she had felt on her mouth were gloves made of lizard skin. Under the rim of the helmet glowed eyes like red embers. The creature spoke:
'Do you want some more?'
And hearing that Fanian had fled in terror, running as fast as she could, until she stumbled on tree-roots in the darkness and collapsed where I had found her.

Fanian was never again the same. The wounds of her body healed, those in her heart did not. She became a mere shadow of her former self. I soon learned that even the most gentle touch made her nervous. Lovemaking was out of the question; she could not relax enough to enjoy it. Gone was the maiden I have described, the one who rejoiced in her flesh.

I knew that I had to do something. I could not help Fanian but if I found the one who had raped her, I might get revenge. I thought long and devised a secret scheme: I knew the monster had come from Utumno, where all that was evil had its origin. I would go there and pretend I had decided to follow Moringotto. Then I would find out what, or who, had raped my fair Fanian. And then, then I would seek my revenge.