The Vultures were the first extraterrestrials the Souls came into contact with. They discovered The Origin, conquered it like they did with other planets, and made life difficult for the souls. However, the Souls found out they could use the Vultures as hosts. They assimilated the Vultures, as well as the inhabitants of the other planets the Vultures conquered. Soon the Souls themselves started spreading and taking over new planets they discovered by replacing their sentient inhabitants. This process was made efficient by Spider technology once the Spiders were assimilated.