Vector Sigma was an ancient supercomputer tied to the origins of the Transformers.
U.S. Animated, Japan
Ancient supercomputer which claimed to predate Cybertron itself. It lay at the core of the planet, presumably put there by the Quintessons, and it brought life to the original Transformers. Vector Sigma laid dormant in the center of Cybertron for eons, only able to be activated by a Key held by Alpha Trion. (Presumably, it was reactivated from time to time, in order to create more new Transformer lives.)
In 1985, Megatron stole the Key from Alpha Trion, and reactivated Vector Sigma to bring life to his Stunticons. The process was repeated by Alpha Trion, who- without a Key- used his own circuitry to activate Sigma. In the process, his intellect merged with that of the supercomputer. After bringing life to the Aerialbots, the amalgamated Sigma/Trion warned Prime about the risk the Key posed to planet Earth.
At some point, Vector Sigma spawned a secondary supercomputer intelligence, the Oracle, which had its own mission for Cybertron's distant future.
Vector Sigma/Alpha Trion remained dormant for several more years after the events involving the Stunticons and Aerialbots. Eventually, it manipulated events in 2007 to create the Headmasters and Targetmasters, ultimately bringing about a new golden age for Cybertron.