Three of Five
Three of Five, Tertiary Adjunct of Unimatrix 01 was a Borg tactical drone, outfitted with a tritanium infrastructure, who formerly served near to the Borg Queen, during the 2350s. 

Prior to his assimilation, Three of Five was a Ktarian male. As Borg drone, he would be identified and tagged by Magnus and Erin Hansen, who deemed him as an extremely important drone. ()

Borg drones
Ktarians