Marrow

The Ship has traveled the universe for longer than any of the near-immortal crew can recall, its true purpose and origins unknown. It is larger than many planets, housing thousands of alien races and just as many secrets. Now one of those secrets has been discovered: at the center of the Ship is . . . a planet. Marrow. But when a team of the Ship's best and brightest are sent down to investigate, will they return with the origins of the Ship—or will they bring doom to everyone on board?