The Halls of Mandos echoed ever louder with the low murmurs of ten thousand thousand souls, collected over the Years and Ages to wait in ponderous repose for their rebirth, or the Dagor Dagorath and the unmaking and remaking of Arda. Miles of glittering tapestry muted the sound only slightly, the fabric set to rippling by the wind of some million sighs and the passage of endless souls. In and out of the halls passed only very few of those who dwelt within—those living elves who had never left the shores of Aman beyond their first landings there, and those who had come later over the seas and the Straight Road when the weight of the ages of the world proved too much to bear up under any more. Few indeed were the number of spirits that drifted from the hall and out across the plains and rivers and forests of Valinor.

In time the waiting spirits within would be reborn, reincarnated into bodies identical to those first crafted for them by the Valar, and sent out to dwell among their fellows within Valinor, in Alqualondë and in Tirion, and in the other beautiful places of that land, though in the time since the Downfall of Númenor near the end of the Second Age, passage back to Middle Earth was denied to those elves who set foot upon the Undying Lands—a law that few if any, having seen the glories of Valinor, would seek to overcome.

For those among the elves who had committed such foul treason as kinslaying, and those that held no love for those remaining in the living world, rebirth was a slow thing in coming, and for some to be withheld until the remaking of the world. For others, those so grievously wounded in life, or laid low by the ravages of centuries and eons of sorrows, the offer to come again in physical form could be denied, and that restful state of disembodiment prolonged, so long as they dwelt within the Far West. Such a fate was rare, but not unheard of, for the elves of Middle Earth had suffered long and in numbers over the Ages at the hands of Melkor and his servants, and the Valar had pity, and could not force a one among them to retake their forms should they not wish it so.

Among those who languished as fëar, as purely spiritual forms with no bodies, was one who sought at last to see more of Valinor than the tapestried, murmuring halls of Mandos' domain. The history of the world played out upon those woven walls for all to see, each great deed recorded as it happened, but in its own way that too was draining. She had died half an age ago, and with her dying words forsook any future life within a body that could know such pain. To watch from afar as Middle Earth suffered, and Men and Dwarves and Elves were born and died in war after war…

She fled the Halls of Mandos as spring came to the mortal world, across the Plains of Valinor (though she skirted the city of Valmar) and the Neverfading Lawns, and through the Gardens of Vána. Within Lórien she found at last a shadow of the rest she sought, lying down as Míriel, the first wife of Finwë, first high king of the Ñoldor, had done in the Years of the Trees so long ago beside those same glittering fountains. For months the spirit drowsed, soothed by the singing of nightingales and the scent of ever-blooming dusk blossoms.

At last as summer began to wax in those mortal realms of Arda she stirred and rose, bidding the silvered willows and faceted lakes a fond farewell for the solace they had given to her wounded and wearied fëa. On and into the Pastures of Yavanna at last she came, thinking now to see herself all of Valinor before returning to the Halls of Waiting. Sibling in nature to the Gardens of Vána, the Pastures were less tempered and more wild, and it stirred the spirit's heart to see them, for in life she had been of the Sindar elves, the Grey elves, and took more joy in the world's natural wonders than in the guided, sculpted gardens that so pleased some of the other clans of the Eldar.

Therein she wandered for a further time, in awe and wonder, and later joy upon the discovery of the spirits of Yavanna's Second-born deep within the Vala's land. Some, like her, had come at the end of their mortal lives upon Middle Earth to dwell at their maker's side, and others, less sure in form, but brighter and with ever increasing energy, lay yet waiting to be born. Those spirits she found nestled among the growing things, tended only barely by the souls of their ancestors, and seemed half tamed, half wild in their nature (though as those spirits made ready to be born into Middle Earth they did happen to settle, to better fit the expectations of their mortal parents).

One such spirit swiftly won the heart of the elf-fëa, for even as it grew it remained restless, wild and vibrant as few within the Pastures did. Its light was a pale greenish-gold, as with all the rest, but it shook and shuddered within its leafy nest as if it could simply not wait to go and be born. To see such joy for life as had long gone out of her own fëa, and that restless, wild nature that seemed as a sister to her own heart? It called to the fëa that sat nearby day after day to watch it grow, and she found herself content to reside in the Pastures of Yavanna until at least such time as the spirit departed to Middle Earth, where she could and would not go.

As summer at last ended and autumn crept in, and August gave way to September, there came a day where by whim or by fate, the fëa came even closer to the budding spirit, and reached out unknowingly and unthinkingly to touch it, her own golden light mingling with the paler, greener glow...and then swirling, speeding into the unborn spirit and mixing, and she cried out, for she could not pull her touch back.

Like a thirsty plant, the growing spirit drank in the energy and light of the fëa, the light of the undying flame that Eru Ilúvatar had lit within all living things. For the light shone forth brighter in the fëa of men and especially elves, being the second and firstborn of Eru, and less luminously within dwarves and ents and all that came later, Eru's adopted children which had been sparked first by the touch of the Valar, and not Eru directly. With a strange, shuddering pulling did fragments of the elf's fëa depart from herself to mingle with that of the growing spirit, increasing its pulse and glow, until in a burst of radiance it flared as a sun, and then vanished, departing down from Valinor to the mortal realm.

In the spirit's wake, the elf Mindonel's fëa was cast down against the soft grass of the Pastures, reeling but unharmed as that small part of herself that had gone into the young spirit drifted further, further, yet further away, until the connection was barely notable as the faintest of threads strung across the stars towards Middle Earth. Back through that gossamer strand Mindonel paused in gathering herself to hear the sound of warm chuckling that faded, at last, into the hearty but tender wail of a child's first cry.

In the west of Middle Earth, at the heart of the Shire, from within a smial nestled snug under The Hill in the middle of Hobbiton, a babe's cry rang out like a peal of laughter. The date was the 8th of September, 1290 by Shire Reckoning, and though the babe had come slightly early, there could be no doubt: Bilba Baggins, the daughter of Belladonna and Bungo Baggins, was born alive and well.

Out across the lands of Eriador, over the Misty Mountains and the rushing Anduin, and deep into the darkness of northern Mirkwood—like an arrow loosed from a bow sprang a lance into the very soul of the woodland king. Those strange elven dreams that count for sleep among the firstborn of Ilúvitar, half waking and half wandering, were shattered like a skin of ice over a deep lake, plunging Thranduil with a gasp back into the waking world. Slender fingers gripped the silken fabric over his heart, the constant ache that had wound about it for near a thousand years gently slackening...

Notes:
Fëa/fëar - soul, spirit (singular, plural, respectively)
Hröa/hröar - body, the physical house of the fëa

Míriel - the first wife of Finwë, the first high king of the Ñoldor; she exhausted herself in childbirth, putting too much of her life essence into Fëanor. She came to Valinor and lay down in the Gardens of Lórien to let her fëa depart her body. Finwë, wanting more children, asked the Valar to remarry. They eventually granted his plea, laying down the laws for elvish remarriage.

Shire reckoning - The Shire was founded in TA1601, so to find the common year, simply add 1600 to any Shire reckoning year, and taadaa! For example, Bilba's birthday is SR1290 + 1600 = 2890 (of the Third Age).