Argus. Killed by Mercury on order of Zeus.
   Argus Panoptes or Argos is a many-eyed giant in Greek mythology. The figure is known for having generated the saying the eyes of Argus, as in to be followed by the eyes of Argus, or trailed by them, or watched by them, etc.
   These terms are used to describe being subject to strict scrutiny in one's actions to an invasive, distressing degree. The monstrous entity has been either directly included or indirectly alluded to in a wide variety of works influenced by Greco-Roman thought over the past several centuries.
   Argus Panoptes, guardian of the heifer-nymph Io and son of Arestor and probably Mycene, was a primordial giant whose epithet, Panoptes, all-seeing, led to his being described with multiple, often one hundred, eyes. The epithet Panoptes was applied to the Titan of the Sun, Helios, and was taken up as an epithet by Zeus, Zeus Panoptes.
   In a way, Walter Burkert observes, the power and order of Argos the city are embodied in Argos the neatherd, lord of the herd and lord of the land, whose name itself is the name of the land. The epithet Panoptes, reflecting his mythic role, set by Hera as a very effective watchman of Io, was described in a fragment of a lost poem Aigimios, attributed to Hesiod: And set a watcher upon her, great and strong Argus, who with four eyes looks every way. And the goddess stirred in him unwearying strength: sleep n
Wikipedia ...