The all seeing. A man with many eyes. Early accounts say he had four eyes, later a hundred. There are many accounts of his parentage. He was in a number of adventures: He killed a bull ravaging Arcadia. He killed a satyr for stealing cattle. He killed Echidna. He avenged the death of Apis.
Argus was killed by Hermes while he guarded Io for Hera
Spawned by Typhoeus and Echidna , the Chimaera had three heads - lion, goat, and snake .Its body was also mixed having the front part of a lion, middle of a goat, and snake for a tail. It breathed fire. It ravaged Lycia, killing cattle and setting fires until it was killed by Bellerophon.
The Cyclopes were gigantic one eyed monsters. There were three of them representing thunder, lighting, and the lighting bolt. They are named Brontes, Steropes, and Arges. They were born to Gaea and Uranus. They were also the first smiths. When Cronus came to power he imprisoned the Cyclopes in Tartarus. The were released by Zeus and fought with him against the Titans. As a reward for their release the Cyclopes gave Zeus his weapons of lighting and thunder. They continued as his workers at Mount Olympus forging his thunderbolts
Apollo killed at least one of the Cyclopes to retribution for Zeus killing his son Asclepius.
A female monster consisting of half nymph, half speckled snake. It lived in a cave coming out to snatch up and eat those passing. The critter was ageless but, not immortal. It was killed by Argus Panoptes while sleeping. It mated frequently with Typhoeus producing a variety of offspring.
Hecatoncheires means "hundred handed". They were gigantic and had fifty heads and one hundred arms each of great strength. There were three of them: Briareus also called Aegaeon, Cottus, and Gyges also called Gyes. They were born to Gaea and Uranus. Their mutual hatred of Uranus caused him to force the Hecatoncheires back into Gaea's womb. This precipitated Gaea's rebellion against Uranus. When Cronus came to power he imprisoned them in Tartarus. The were released by Zeus and fought with him against the Titans. They were able to hurl huge boulders as many as a hundred at a time against their opponents. One of them, Briareus, served as Zeus's bodyguard.
The Giants were generated from Uranus blood resulting from his castration by Cronus. They became powerful enough to try to unseat Zeus and the Olympians. When the gods won they imprisoned the Giants in Tartarus.
These are female monsters with snakes for hair. Their faces are so ugly that any man that see the face will turn to stone. Oddly the three gorgons have very different origins. Stheno and Euryale were born as gorgons from Phorcys and Ceto. They are immortal. Medusa was not.
Medusa began life as a girl so lovely she made Athena jealous. Such beauty turned Poseidon's head. He seduced the girl but, unfortunately for her did so in one of Athena's temples. Such an affront to Athena would not go unpunished particularly by one already in ill favor. So Medusa was turned by Athena into a gorgon. Since she started as human she remained mortal. As if this were not punishment enough, Athena later helped Perseus hunt her down and kill her.
When Perseus cut her head off Pegasus and Chrysaor, her children by Poseidon, sprang forth. Drops of her blood fell into the Libyan desert and turned into snakes. Later one of these snakes killed Mopsus. After Perseus left with her head Athena took charge of what was left of her body. She flayed off Medusa skin and made it into her trademark Aegis. She two drops of the blood to King Erichthonius explaining that one would cure disease and the other was a deadly poison. She gave a lock of the hair Heracles hidden in an urn.
The Ash Tree Nymphs were generated from Uranus blood resulting from his castration by Cronus .
Typhoeus, was a fire breathing dragon with a hundred heads that never rest. It was birthed by Gaea as a last ditch effort to keep the Olympians from defeating her children the Titans. It came close to succeeding, setting most of the gods to flight and capturing Zeus. Hermes was able to free Zeus. Zeus was then able to dispatch Typhoeus with his lighting bolts. Typhoeus is buried under Mount Etna in Sicily.
Cerberus is one of the offspring of Typhoeus and Echidna. It is a three headed dog with a snake tail and snake heads proturding from his back. He guards the entrance to the underworld, allowing the dead to enter but, never to leave. One of the few living mortals to get past Cerberus was Orpheus who charmed it to sleep with his song during his attempt to rescue Eurydice from death. Fetching Cerberus from the underworld and displaying him to King Eurystheus was the last labor of Heracles .
The Sirens are sisters who lure sailors to their death. The song of the Sirens is irresistible but, the they reside beyond impassable reefs which destroy the sailors boat when they try to reach the Sirens. Among those tempted were Jason on the Argo and Odysseus.
Pegasus was a winged horse and good flyer. The Pegasus was the result of the ill fated mating of Medusa and Poseidon. It was born from Medusa when her head was cut off by Perseus. Tamed by Bellerophon it served as his mount during his adventures including his slaying of the Chimaera. When Bellerophon attempted to fly Pegasus to Mount Olympus he was dismounted by Zeus. Pegasus continued on and made it to Mount Olympus. Here Pegasus spent his days carrying lighting bolts for Zeus.
Chrysaor was the result of the ill fated mating of Medusa and Poseidon. He was born from Medusa when her head was cut off by Perseus. Little is known of Chrysaor other then he was considered a stout hearted warrior. His name means Golden Sword. He fathered Geryon. His appearance is unknown but, given his family it is likely to have been unusual. He was possibly a giant.