Theron was an Argolin warlord.
Forty years before the Fourth Doctor arrived on the Leisure Hive, Theron began a campaign of conquest starting a very brief war with their neighbours the Foamasi. His ambition all but destroyed the planet and left its people sterile and short-lived. He may have died in the conflict. His helmet hung in the chairman's conference room. (DW: The Leisure Hive)