Presiding over the Zerg was the Overmind, now replaced by Sarah Kerrigan, the Queen of Blades. To efficiently control the Swarm, the supreme Zerg master requires the aid of its leader-servants, the Cerebrates, and also of lesser but nevertheless important agents. The space-faring species of the Gargantis Proximae was assimilated into the Swarm as the Overlords, vital commanders who direct the will of Cerebrates and the Queen of Blades into the myriad number of quasi-soulless Zergs, making them act as one unstoppable and intelligent hive-minded host. Without the steering presence of Overlords, a Brood cannot grow, or dominance would spiral out of control.

Overlords of before could detect invisible or burrowed units, but it appears this role has been passed on to an evolutionary variant – the Overseer.

Currently, Overlords are slow moving behemoths that cannot detect. However, they are still the base zerg scouts and excel at this role in the early stages of any zerg colony.