The Croke, while engaging in a vicious civil war among their own kind, introduced Lugubraa soldiers to their homeworlds in the Croke Reach. The Lugubraa proved so tenacious and deadly that for over 300 years, they spread, destroying Croke settlements across the region, no longer under the control of their original employers. The Croke sought the help of the cloners of Kamino, believing that they needed to fight the Lugubraa with members of their own kind. The Kaminoans created a genetic variant. The Croke called this new force the "Leech Legion", but these clones proved to be just as deadly to the Croke as their predecessors.
At some point during the Clone Wars, the Leech Legions attacked the planet Niorde. In an effort to protect their world, several scouts of the native Niordi traveled to a secret laboratory and underwent a radical cybernetic alteration to become living weapons. Several of those scouts perished during the experiment and before the survivors were operational, the Leech Legions had overrun Niorde. The remaining cyborg artillery units attacked the enemy flagship, and only D'harhan, a Niordi living weapon, survived the confrontation.