Fate of Worlds (2012) is the fifth and final book written in the Fleet of Worlds series, itself a subset of Larry Niven's Known Space series. The novel was coauthored by Edward M. Lerner.
Fate of Worlds opens as (from the Ringworld series) Ringworld's Children closes, which is decades after Betrayer of Worlds, the prior book in the Fleet of Worlds series. The novel thus concludes both series, and involves characters from both.