Originally parasitic creatures on the original Zerg homeworld of Zerus, The Overmind incorporated Cerebrates into the Zerg to help him command and control the Swarm. Cerebrates instituted a rigid power hierarchy within the Zerg and directed Zerg evolution.
During the events of the Great War, Cerebrates continued to be crucial intermediaries for enforcing the Overmind's will until the Protoss discovered that Cerebrates could be permanently killed using Dark Templar energy. After Dark Templar Zeratul killed the first Cerebrate, Zasz, on Char, Cerebrates became targets of Protoss and Terran attacks, causing many to perish.
After the death of the first Overmind on Aiur, the Cerebrates a few Cerebrates led by Daggoth merged to create a second Overmind, which the United Earth Directorate Expeditionary Force later enslaved. After Kerrigan engineered the destruction of the second Overmind using Zeratul, she hunted down and killed all remaining Cerebrates so exert her complete control over the Swarm.
Role within the Swarm
Cerebrates act as intermediaries between the Overmind, who embodies the collective will of the Swarm, and Overlords, who disseminate the Cerebrate's commands individual Zerg minions. Each Cerebate commands a single Zerg brood and is bound to execute a specific role as dictated by the Overmind. If a Cerebrate is incapacitated or killed, the brood loses its link with the Overmind; without this direct control, the brood becomes aimless, reckless, and destructive.
When the physical manifestations of a Cerebrate is destroyed by conventional means, the Overmind can resurrect it with the same personality, memories, and qualities. Cerebrates can be permanently killed by Dark Templar energy.
Cerebrate are powerful psychics, allowing them to feel the presence of creatures and entities at a great distance, and even influence them. Being psychic creatures, Cerebrates are able to maintain telepathic contact with the Overmind, other Cerebrates, and their minions. This ability allows them to relay the Overmind's orders and command their broods at a great distance.