Fate of worlds : return from the Ringworld

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. Now, without warning, the Ringworld has vanished, leaving behind three rival war fleets. If the fallen civilization of the Ringworld can no longer be despoiled of its secrets, the puppeteers will be forced to surrender theirs.