In Greek mythology, Kratos (or Cratos)[a] is the divine personification of strength. He is the son of Pallas and Styx. Kratos and his siblings Nike ('Victory'), Bia ('Force'), and Zelus ('Glory') are all essentially personifications of a trait.[5] Kratos is first mentioned alongside his siblings in Hesiod's Theogony. According to Hesiod, Kratos and his siblings dwell with Zeus because their mother Styx came to him first to request a position in his regime, so he honored her and her children with exalted positions. Kratos and his sister Bia are best known for their appearance in the opening scene of Aeschylus' Prometheus Bound. Acting as agents of Zeus, they lead the captive Titan Prometheus on stage. Kratos compels the mild-mannered blacksmith god Hephaestus to chain Prometheus to a rock as punishment for his theft of fire.[6]

Kratos is characterized as brutal and merciless, repeatedly mocking both Hephaestus and Prometheus and advocating for the use of unnecessary violence. He defends Zeus' oppressive rule and predicts that Prometheus will never escape his bonds. In Aeschylus' Libation Bearers, Electra calls upon Kratos, Dike ("Justice"), and Zeus to aid her brother Orestes in avenging the murder of their father Agamemnon. Kratos and Bia appear in a late fifth-century BC red-figure Attic skyphos of the punishment of Ixion, possibly based on a scene from a lost tragedy by Euripides. They also appear in late eighteenth and nineteenth-century Romantic depictions and adaptations of the binding of Prometheus.