The Ji'atrix are an ethereal xenos species that has been annexed by the T'au Empire.
They're known for their affinity for the void and skill at spacefaring. This has led to their use as scouts into the gravity ravaged depths of the Black Reef, in the Canis Salient of Jericho Reach, together with the Nicassar.
Their efforts have succeeded in mapping a number of routes through the edges of the Reef, at least on the T'au side of the anomaly, allowing the Kor'vattra ships more tactical flexibility than those of their enemies and also allowing them to lay deadly ambushes within the edge of the Stygian Break.
Sources
- Deathwatch: The Achilus Assault (RPG), pg. 130.