Phssthpok is a protector stage Pak. Bereft of bloodline in a war on the Pak homeworld, Phssthpok moved into the Pak Library in an attempt to discover some knowledge that would enable him to go on living despite having lost his original purpose.
Phssthpok discovers records of a Pak colony in the arm of the galaxy, and its probable failure. He works out that the soil of Earth lacks thallium oxide, and mounts a rescue mission aboard a ramship and spends the majority of the next 20,000 Earth years traveling to the target system of the colony (Sol System.) He arrived in 2125 and kidnapped Jack Brennan, fed him Tree-of-Life root and turned him into a protector. Phssthpok underestimated the Brennan Protector however and was eventually killed by his former captive.