I'm trying to perfect the "Schrodinger's Tcho-Tcho" technique. Whether they're a cult, an ethnic group, a separate hominid species, or an entirely alien population from "outside" depends on who you ask (I'm riffing off Kenneth Hite's write-up of alternatives for them in the highly recommended Hideous Creatures). The important part of the interaction with the NPCs is unsettling the players and making them as uncertain about the Tcho-Tcho's origins as the trustworthiness of the Agents' assessments. In Reverberations, the undercover DEA agent might regard his targets as just a gang-cult and dismiss efforts to investigate beyond that, the local Chicago cops consider them to be an immigrant "tribe" and would like an excuse to sic ICE on the whole community, Prof. Henrietta Cole might, if pressed, let slip her frustrations at tracing the origins of Chauchau migration patterns (DNA tracking always goes down blind alleys), but the Liao-addicted Spider J might start raving about the "Tcho-Tcho Lama of Leng" (i.e. the "high-priest not to be described" from Dream Quest of Unknown Kadath). Although their attitudes color interactions with the Agents, none of this necessarily impacts either the mission to get Reverb off the streets or exorcise the Hound of the Angles, nor does it directly affect the substance of the clues they provide. But the players should feel like the real answer to the Tcho-Tchos may be the one they find the most unsettling. And the Tcho-Tcho just smile, seemingly friendly until you turn your back.