Prometheus Bound is an Ancient Greek tragedy based on the myth of Prometheus, a Titan who defies the gods, and gifts humanity with fire, for which he is subjected to eternal punishment. At the beginning, Kratos, Bia, and Hephaestus chain Prometheus to a mountain in the Caucasus. A chorus of Oceanids appear, attempting to comfort Prometheus by conversing with him. Prometheus cryptically tells them that he knows of a potential marriage that would lead to Zeus's downfall. After a visit from Io, Hermes comes to him, demanding that Prometheus tells him who it is that threatens to overthrow Zeus. Prometheus refuses, and Zeus strikes him with a thunderbolt that plunges Prometheus into the abyss.