"Green Eyes" was a Gargantis proximae alive when the entire species was willingly assimilated into the Zerg Swarm. When Kerrigan fell, Green Eyes was released from the zerg hive mind, and found that the only other gargantis proximae that had survived the centuries was his purple-eyed mate.
After Caston Gage, a Dominion marine attached to Meatbag Squadron killed "Purple Eyes", "Green Eyes" took control of local feral zerg and eliminated the marines occupying the abandoned Ghost Academy on Tarsonis one by one, but left Caston alive in the hopes that the marine would kill him as well. Caston did not.
Grieving for his lost mate, "Green Eyes" returned to the swarm, hoping to forget what he had lost.