For decades, the spacefaring species of Known Space have battled over the largest artifact--and grandest prize--in the galaxy: the all-but-limitless resources and technology of the Ringworld. But without warning the Ringworld has vanished, leaving behind three rival war fleets.
"Something" must justify the blood and treasure that have been spent. If the fallen civilization of the Ringworld can no longer be despoiled of its secrets, the Puppeteers will be forced to surrender theirs. Everyone knows that the Puppeteers are cowards.
But the crises converging upon the trillion Puppeteers of the Fleet of Worlds go far beyond even the onrushing armadas:
Adventurer Louis Wu and the exiled Puppeteer known only as Hindmost, marooned together for more than a decade, escaped from the Ringworld before it disappeared. And throughout those years, as he studied Ringworld technology, Hindmost has plotted to reclaim his power ...
Ol't'ro, the Gw'oth ensemble mind--and the Fleet of World's unsuspected puppet master for a century--is deviously brilliant. And, increasingly unbalanced ...
Proteus, the artificial intelligence on which--in desperation--the Puppeteers rely to manage their defenses, is outgrowing its programming. And the supposed constraints on its initiative ...
Sigmund Ausfaller, paranoid and disgraced hero of the lost human colony of New Terra, knows that "something" threatens his adopted home world. And that it must be stopped ...
Achilles, the megalomaniac Puppeteer, twice banished--and twice rehabilitated--sees the Fleet of World's existential crisis as a new opportunity to reclaim supreme power. Whatever the risks ...
One way or another, the fabled race of Puppeteers may have come to the end of their days in "Fate of Worlds, "the final installment to Larry Niven and Edward M. Lerner's "Fleet of Worlds "series.

"Fleet of Worlds" marks Larry Niven's first full novel-length collaboration within his Known Space universe, the playground he created for his bestselling Ringworld series. Teaming up with fellow SF writer Edward M. Lerner, "Fleet of Worlds" takes a closer look at the Human-Puppeteer (Citizens) relations and the events leading up to Niven's first Ringworld novel. Kirsten Quinn-Kovacs is among the best and brightest of her people. She gratefully serves the gentle race that rescued her ancestors from a dying starship, gave them a world, and nurtures them still. If only the Citizens knew where Kirsten's people came from....
A chain reaction of supernovae at the galaxy's core has unleashed a wave of lethal radiation that will sterilize the galaxy. The Citizens flee, taking their planets, the Fleet of Worlds, with them.
Someone must scout ahead, and Kirsten and her crew eagerly volunteer. Under the guiding eye of Nessus, their Citizen mentor, they explore for any possible dangers in the Fleet's path--and uncover long-hidden truths that will shake the foundations of worlds.