In Greek mythology, which monster did Hermes help Zeus defeat by killing its many eyes?

In Greek mythology, Hermes killed Argus Panoptes, the many-eyed monster who guarded Io.

Argus Panoptes was a giant whose name means “all-seeing.” Hera appointed him to watch Io, a woman transformed into a heifer after Zeus became involved with her. Because Argus’s many eyes allowed him to remain constantly vigilant, he was a formidable guardian.

Zeus sent Hermes to rescue Io. Hermes used music, storytelling, and other forms of persuasion to lull Argus to sleep, then killed him. Hera later commemorated Argus by placing his eyes on the feathers of the peacock in some mythological accounts.

The episode differs from the story of Typhon, Zeus’s gigantic enemy, and from the dragon Ladon, who guarded the golden apples. Those creatures are sometimes mixed together because all appear in Greek monster myths.