The Delorf were—supposedly—a sapient species native to the Galactic Core, but they may merely have been a figment of Imperial Intelligence's internal mythology, where they figured in a story which purported to explain the name of the Renik counterintelligence branch.
According to the story current among Imperial Intelligence operatives, the Delorf were a low-technology herbivorous species, who survived through a relatively widespread ability to detect and negate hostile intent in others, perhaps a form of Force technique. When the Delorf "sensitives" detected a threat, they gathered in a ritual known as Renik, which purged the hostility from the individual in question, "making him one of the Delorf in mind if not in body".
Although it is not explicit in the extant Imperial accounts, this phrase suggests that the Renik was primarily used against non-Delorf, and aided the survival of the species in the heavily industrialized and high-tech Core by brainwashing interstellar visitors to their homeworld, and forcing them to join the Delorf herd-mentality.
An Imperial Security Bureau report included in The Imperial Sourcebook dismisses this story, however, and says that "Renik" was simply the name of Admiral Kiner turned back-to-front, a pun on the fact that it was a counter-intelligence agency. It is thus unclear how much any of the information on the Delorf current within Renik was true.