The Well of Stars — Robert Reed

The Great Ship, so vast that it contains within its depths a planet that lay undiscovered for generations, has cruised through the universe for untold billions of years. After a disastrous exploration of the planet, Marrow, the Ship's captains face an increasingly restive population aboard their mammoth vessel.

And now, compounding the captains' troubles, the Ship is heading on an irreversible course straight for the Ink Well, a dark, opaque nebula. Washen and Pamir, the captains who saved Marrow from utter destruction, send Mere, whose uncanny ability to adapt to and understand other cultures makes her the only one for the job, to investigate the nebula before they plunge blindly in. While Mere is away, Pamir discovers in the Ink Well the presence of a god-like entity with powers so potentially destructive that it might destroy the ship and its millions.

Faced with an entity that might prevent the Ship from ever leaving the Ink Well, the Ship's only hope now rests in the ingenuity of the vast crew . . . and with Mere, who has not contacted them since she left the Ship...