Species 571

From Memory Alpha, the free Star Trek reference

Species 571 was the Borg designation for a race of the Delta Quadrant who worship a god named Brothara. They were a humanoid species distinguished by a bifurcating (cartilaginous) ridge running vertically down the forehead stopping at the nose.

Members of this species came into contact and were assimilated by the Borg sometime before 2368, when a Borg sphere crashed on Planet 1865-Alpha, severing the three surviving Borg drones from the Collective. Among the drones were P'Chan and Lansor, both of whom managed to escape the Collective permanently some time before 2376.