They were first encountered by Earth Starfleet during the 2250s. (ENT: "Two Days and Two Nights") By the 2370s they had encountered the Borg, and a number of their species had been assimilated as Borg drones by 2377. (VOY: "Unimatrix Zero, Part II") While neither Ravis or Axum were given a species name, they appear to share the same make-up. The novel Acts of Contrition calls this species the "Mysstren" and reveals that they have low-level psionic abilities.