Argus Panoptes

Argus Panoptes was a watchman with a hundred eyes.

Hera set Argus to watch Io, who had been transformed into a cow. Hera wanted to keep Zeus away from Io. With a hundred eyes watching Io, Zeus had no hope of spiriting Io away without detection from Argus. Even when Argus slept, some of his eyes would continue to watch while the rest of the eyes were closed.

Argus Panoptes Guarding the Heifer (Io)
Red Figure pitcher, c. 460 BC
Museum of Fine Arts, Boston

Zeus decided to send his resourceful son, Hermes. Hermes was dressed as a shepherd. Hermes lulled Argus to sleep, and then the god killed the watchman with his sword.

Hera rewarded Argus for his service by placing his eyes on the tail of the peacock, which was her favourite bird.

Argus Panoptes had also been credited for killing the monster Echidna.