WARNING: This faith has not yet had a chance to become canonical.
Rhatujaro best translated as Seekers of Truth (from rhatus (to search) and jaro (truth)), is an extinct kavkem mythology that enjoyed being the dominant faith on Vatenas before Nayabaru technological advances began to lay waste to kavkem curiosity.
Rhatujaro is what you get if you raise a culture of sceptics in an environment where tangible evidence of 'gods' exist: Evidence-based religion.
The difference between Rhatujaro and atheism was a slightly too eager attribution of mystical powers to distant players in the conflict, and an indifferent shrug when asked to perhaps outright toss out unfalsifiable aspects such as Garukaron, which they definitely refused to let go of - chiefly using the reasoning that the other gods had to come from somewhere, and a purely physical universe wouldn't really cut it.
The believers of Rhatujaro were highly willing to go out and collect evidence on more dangerous elements of the world, which brought them very close to Nayabaru settlements and occasionally inspired them to kidnap a Nayabaru to question them. This curiosity eventually got enough of them captured as Nayabaru technology improved, causing the belief to become more and more fringe, until it was eventually memetically subsumed by Ne͡imakanaas̈ (which essentially claims that there is no evidence to collect, which is a far safer headspace for kavkema to live in).
As the only of the Taaravahr-derived religions, some minor strains of Rhatujaro acknowledged the existence of Ysikary as Syeesa (from syees, to warn/threaten). However, given Ysikary's nature, this would have been based purely on indirect evidence.
Syeesa was considered a goddess of yria (life of suffering/slavery). The Nayabaru were attributed to her actions, not to those of their Tkanetar, Terenyira or mere circumstance. Any stories told about her have since culturally merged into Tkanetar or simply disappeared.
As already mentioned, the believers of Rhatujaro believed in collecting as much evidence as they could on the true nature of the universe and the deities it contained. A standard coming of age ritual was to send a kavkem out into the world, then let them return once they had learnt something about it that their ryrhakenem did not know.