City At The End Of Time by Greg Bear

in the Broken Tower, still the preserve of the greatest and most curious Eidolon of all.
    Work on the Tiers resumed, with a new, redesigned population of ancient breeds set in place of the old. A young Mender of no special distinction, Ghentun was summoned to Malregard, interviewed by angelins, and chosen to be Keeper of the Tiers—and that was that. There was no contest, no list of applicants.
    Like many of the young Menders of that era, he had converted to noötic mass—fashionably giving up his gens inheritance. Yet to accept the position of keeper, the Librarian’s epitomes insisted he must reconvert—he must become primordial again.
    In the process, something went wrong. While retaining his knowledge of history, he lost all personal memories. The old Ghentun vanished; the new was born. Yet how could he have regrets? Mere Menders did not question the decisions of Great Eidolons.
    Sometimes, when Ghentun watched his breeds sleep, they would shiver with a strange resonance, as if listening to death-cries out of the deep and broken past—sensing their compatriots, made of the same ancient matter, flesh of the same flesh, crawling along their mashed and bundled fates, until they reached the severed ends—and fell into the dimensionless maw of the Typhon. As they had been designed to do. Canaries in a coal mine.
    Proving—if true—that the Tiers were not the idle toy of a demented Great Eidolon, but the one last, true chance to save their tiny scrap of universe.

    Finished with his inspection, Ghentun ascended in secured lifts through the outer thick walls to the source of all breeds, the crèche, high above the Tiers.
    At the outer circle of the crèche, the Keeper made his signs of respect before the fluid, light-absorbing draperies. Beyond lay the Shaper’s rotating nurseries, where hundreds of new-made breeds slept in quiet rows, awaiting their nativity—should it ever arrive. The curtains swung wide and a golden light spilled over, warming the Keeper’s skin. He had always enjoyed seeing where his breeds were formed, nurtured, and subliminally instructed through infancy, then prepared for transport to the Tiers by the umbers—slender grayish-brown wardens, low and swift.
    Several of these umbers met Ghentun beneath the wide sweep of the Shaper’s pallid caul. Two escorted him through the caul—proceeding without escort might subject him to unpredictable fields and pressures—and higher still, between green curtains of gel and tall, eerily still cylinders of primordial ice—into the lambent mist of the vitreion, the Shaper’s inner sanctum—where machines could not go. Here, on natal pads arranged in counterrotating spheres, the golden glow intensified. Spin-foundries like frantic bushes—all silvery vector-curves and whirling branches—surrounded and refined a dozen half-formed infants, their motions so rapid Ghentun could not track them at his highest frequency. The last Shaper in the Kalpa, the crèche’s mistress of birth stood on six slender legs beside an elevated natal pad. At Ghentun’s approach, her small head popped up from a radiance of dark, field-wrapped tool-arms. Shapers and Menders had long since parted ways in physical appearance. She acknowledged his presence, then finished imprinting an early layer of mental properties into a small, quivering thing covered in fine white fur, its large eyes tightly shut, though its lips moved continuously, as if it might awake at a whisper.
    The Shaper put away her kit and joined Ghentun on a walk through the prototypes annex.
    “I’m not sure what more can be done,” she said as they slid between the history pallets, on which were suspended most of the second-stage proposals for the inhabitants of the Tiers—a sobering record of extended development, indecision, and failure. Ghentun himself had made a number of significant mistakes early in his tenure.
    He transferred his notes to the Shaper, who read them with several of her many eyes.
    “No