Great Leader

 was a computer that ruled Zordin (later Atlantis) and a dozen other planets at some point in history. He forbade all knowledge of events before "Year Zero", which was the start of his rule. (AUDIO: Year Zero)

He taunted Bernice Summerfield, Leonidas and Ruth when they entered Poseidon's labarynthe. He told them about The Epoch. (AUDIO: The Temple of Questions)