The daughter of Phorcys and Ceto, Stheno was born in the caverns beneath Mount Olympus. Of the three Gorgons, she was known to be the most independent and ferocious, having killed more men than both of her sisters combined. In Greek mythology, she was transformed into a Gorgon because of standing with her sister Medusa, who was raped by the sea god Poseidon in the Temple of Athena. Athena bearing no emotion and finding no fault in Poseidon, was furious with Medusa. As a punishment, Medusa was changed into a terrible monster, along with her sisters Stheno and Euryale. Stheno tends to be depicted as a thin gorgon monster with red snakes curling around her head instead of hair, however earlier accounts describe her as having a scaly head, a boar's tusks, bronzed hands, a protruding tongue, glaring eyes and a snake around the waist as a belt.
When the gorgon Medusa was beheaded by Perseus, Stheno and Euryale tried to kill him, but failed due to his use of Hades' cap, becoming invisible.