Brontes, Steropes, and Arges (the three descended from Gaia and Uranus) were the inventive blacksmiths of the Olympian gods. They were skilled metal workers and created Zeus' thunderbolts, Poseidon's trident, and Hades' Helmet of Darkness that was later used by Perseus while on his quest to decapitate Medusa. However, they spent the majority of their early existence imprisoned. Their father Uranus (sky) hated all of his offspring (the Titans, Cyclopes, and Hecatonchires or hundred-handers) and kept them confined deep within Gaia (earth). The defeat of Uranus by his son Cronus (a Titan) freed the Cyclopes for a time, but Cronus was a paranoid ruler. He feared the Cyclopes' power and cast them into Tartarus (the place of punishment in the underworld) where they remained imprisoned until Zeus (an Olympian and son of Cronus) released them, requiring their aid in the Titanomachy (battle of the Titans). With the assistance of the Cyclopes and their thunderbolts, Zeus overthrew Cronus and the Titans and became ruler of the cosmos. He was grateful for the Cyclopes' help and allowed them to stay in Olympus as his armorers and helpers to Hephaestus, god of smiths. The Greeks also credited them with building the massive fortifications at Tiryns and Mycenae in the Peloponnese.
Brontes, Steropes, and Arges are mainly mentioned in passing in most of the myths to convey strength in heroes and the fine quality of weapons but are major characters in one other event – their deaths at the hands of Apollo. Zeus struck Asclepius, Apollo's son, down with a thunderbolt for having risen a person from the dead. Apollo was outraged and killed the Cyclopes who had forged the deadly thunderbolt. It appears that Apollo's rage was misplaced, yet by killing the Cyclopes, he was indirectly punishing Zeus. The ghosts of Brontes, Steropes, and Arges are said to dwell in Mt. Aetna, an active volcano that smokes as a result of their burning forges.
The second generation of Cyclopes was a band of lawless shepherds living in Sicily who had lost the skill of metallurgy. Polyphemus, son of Poseidon and the sea nymph Thoosa, is the only notable individual of the lot and figures prominently in Homer's Odyssey. Odysseus and his crew landed on Sicily, realm of the Cyclopes. He and a few of his best men became trapped in Polyphemus' cave when Polyphemus rolled a large boulder in front of the entrance to corral his sheep while Odysseus was still inside. Polyphemus was fond of human flesh and devoured many of the men for dinner. On the second night, Odysseus told Polyphemus that his name was "Nobody," and tricked him into drinking enough wine to pass out. While he was incapacitated, Odysseus/Nobody blinded him with a red hot poker. Polyphemus shouted in pain to the other Cyclopes on the island that "Nobody" was trying to kill him, so no one came to his rescue. Eventually, he had to roll away the stone to allow his sheep to graze. Odysseus and the remaining crew clung to the bellies of the exiting sheep where Polyphemus could not feel them as they passed him on their way to pasture and escaped. As Odysseus sailed away from the island, he shouted to Polyphemus that it was Odysseus who had blinded him. Enraged, the Cyclops threw huge boulders at the ship and shouted to his father, Poseidon, to avenge him.
Recent scholars have hypothesized about the origin of the Cyclopes' single eye. One possibility is that in ancient times, smiths could have worn an eye patch over one eye to prevent being blinded in both eyes from flying sparks. Also, smiths sometimes tattooed themselves with concentric circles which could have been in honor of the sun which provided the fire for their furnaces. Concentric rings were also part of the pattern for making bowls, helmets, masks, and other metal objects. Notice that the first generation Cyclopes were associated with metal-working while the second generation was not. Apparently, the lawless band of Cyclopes is a later addition to the myths. The incidence with Polyphemus seems to have had an independent existence from the Odyssey before Homer added it to his epic adventure. It was probably told as a separate myth at certain functions.
It is uncertain why the Cyclopes were demoted from the smiths of the gods to a lawless group of monsters with no reverence for the gods. When the universe came into being, there were many monsters and vague forms that were gradually replaced with beings with more human forms. Order was replacing chaos. The monsters were phased out, and this could have lead to the transformation of the "good" Cyclopes to the "evil" Cyclopes that were destined to be fought and defeated by the divine human form.