Ringworld series

Pierson's puppeteers, strange, three-legged, two-headed aliens, have discovered an immense structure in a hitherto unexplored part of the universe. Frightened of meeting the builders of such a structure, the puppeteers set about assembling a team consisting of two humans, a puppeteer and a kzin, an alien not unlike an eight-foot-tall, red-furred cat, to explore it. The artefact is a vast circular ribbon of matter, some 180 million miles across, with...

A cross-over conclusion to the Ringworld and Fleet of Worlds series finds the Puppeteers of the Fleet of Worlds targeted by rival war fleets after the disappearance of the Ringworld, prompting exiled Puppeteer Hindmost to draw on his knowledge of Ringworld technology to reclaim his power.