Hephaestus Systems was an American manufacturing company responsible for manufacturing the Antimatter Bombs and GAULEM robots (including Luna and G-OLM). The GAULEMs were used by Zero Sr. during the Nonary Game: Ambidex Edition. The bombs were used by the Myrmidons, and passcode technology was applied to them by an engineer from the company, under Dio's orders.

The term "Hephaestus Systems" was referred to by the director in the answers, as well as the GAULEM entry in the Secret Archives.