They wished to exterminate humanity and all of the other races, who they viewed as inferior and undeserving of life. However, they were unable to produce enough offspring to mount such an attack. Their birth rate being the lowest of any sentient species in that area of the galaxy, they decided to use genetically modified human embryos to create Pitar fetuses.
They sought to eradicate humanity and other species deemed inferior and unworthy. Due to a low birth rate among sentient beings in that galaxy sector, they resorted to using modified human embryos to produce Pitar fetuses.