Protector

Protector is a 1973 science fiction novel by American writer Larry Niven, set in his Known Space universe. It was nominated for the Hugo in 1974, and placed fourth in the annual Locus poll for that year.The work fleshes out a species called the Pak, originally introduced in a 1967 story called "The Adults", which forms the first half of the novel (there titled Phssthpok); the second half is titled Vandervecken. The Pak also appear in several of Niven's later works, including the later volumes of the Ringworld series and the novel Destroyer of Worlds which serves as a semi-sequel to Protector.