Thousands of years ago, so we eventually learn, the omnipotent and now-vanished Preservers built Confluence, not a planet but a habitat, or construct, that's home to a zillion species--""bloodlines""--whose ancestry includes both human and animal genes. When Yama, a boy of mysterious origin, was found resting on the breast or a dead woman in a boat, he was adopted by the Aedile, ruler of the city Aeolis and of the vast, crumbling necropolis that surrounds it. Now, the sinister apothecary Dr. Dismas visits the great city Ys and learns something significant about Yama's origins--but he won't tell the Aedile what it is; indeed, Dismas attempts to kidnap Yama and involve him in the war against the ""heretics,"" adherents of the enigmatic and recently vanished Ancients of Days. Yama escapes Dismas and in the necropolis acquires a sentient knife that feeds on sunlight. The Aedile resolves to place Yama as a clerk with Prefect Corin in Ys, but Yama, finding he can mentally control machines, joins up instead with potboy Pandaras and agrees to assist the warrior Tamora with her commission to track down a spaceman who's jumped ship. Yama defeats the corrupt, powerful spaceman by unexpectedly summoning a feral machine. Eventually, Yama will learn that he's a Builder, one of a race created to serve the Preservers; but to learn the rest of his own identity and heritage, he must force his way into the jealously guarded Palace of the Memory of the People. Agreeably meaty and complex, challenging and tantalizing: an entry with ample scope for sequels, the one possible drawback being that McAuley's (Pasquale's Angel, 1995, etc.) narrative voice may be too cool to be entirely satisfying.