This is the universe. Big, isn't it?
The Investigators were taken from the crèches of Mictlan by the Celestis to populate an "agency" dedicated to the Celestis' interests in the Inner Sea. They were psychotic detective/assassins, who could change their physical appearance and move spatiotemporally at will. Their "default" appearance was of a human-shaped "gap in history."
The Investigators had a rigid hierarchical system, in which those of the highest rank were referred to by the smallest number, so that the most senior was always named One.
Although in most respects the Investigators had their personalities ruthlessly cauterised by the Celestis, they still often retained an individual, twisted sense of humour. Investigator Eighteen, for instance, always made new servants undergo a sham trial in which they attempted to justify their right to exist in front of a jury of the dead of their world. But the trials inevitably ended in the subject's enslavement in Mictlan. (PROSE: Investigators)