Cyclopes
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 thunerbolts
Arges was killed by Hermes while he guarded Io for Hera
Apollo killed at least one of the Cyclopes to retribution for Zeus killing his son Aesculapius.
Hecatoncheires
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 hatered of Uranus caused him to force the Hecatoncheires back into Gaea's womb. This parcipatated Gaea's rebellion against Uranus. When Cronus came to power he imprisoned the Cyclopes 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 bodygaurd.
Giants
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 early in their rule. When the gods won they imprisoned the Giants in Tartarus.
Ash Tree Nymphs
The Ash Tree Nymphs were generated from Uranus blood resulting from his castration by Cronus.
Typhoeus
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
Cerberus is the three headed dog with a dragon tail which guards the entrance to the underworld. Allowing the dead to enter but, never leave. Fetching Cerberus was the last labor of Heracles.
Sirens
The Sirens are sisters who lure sailors to their death. The song of the Sirens is irrestable but, the they reside beyound unpassable reefs which destroy the sailors boat when they try to reach the Sirens. Among those tempted were Jason on the Argo and Odysseus.
MONSTERS AND GIANTS
MONSTERS, in the language of mythology, were beings of unnatural proportions or parts, usually regarded with terror, as possessing immense strength and ferocity, which they employed for the injury and annoyance of men. Some of them were supposed to combine the members of different animals; such were the Sphinx and Chimaera and to these all the terrible qualities of wild beasts were attributed, together with human sagacity and faculties. Others, as the giants, differed from men chiefly in their size; and in this particular we must recognize a wide distinction among them. The human giants, if so they may be called, such as the Cyclops, Antaeus, Orion, and others, must be supposed not to be altogether disproportioned to human beings, for they mingled in love and strife with them. But the super-human giants, who warred with the gods, were of vastly larger dimensions. Tityus, we are told, when stretched on the plain, covered nine acres, and Enceladus required the whole of Mount AEtna to be laid upon him to keep him down.
We have already spoken of the war which the giants waged against the gods, and of its result. While this war lasted the giants proved a formidable enemy. Some of them, like Briareus, had a hundred arms; others, like Typhon, breathed out fire. At one time they put the gods to such fear that they fled into Egypt and hid themselves under various forms. Jupiter took the form of a ram , whence he was afterwards worshipped in Egypt as the god Ammon, with curved horns. Apollo became a crow, Bacchus a goat, Diana a cat, Juno a cow, Venus a fish, Mercury a bird. At another time the giants attempted to climb up into heaven, and for that purpose took up the mountain Ossa and piled it on Pelion.* They were at last subdued by thunderbolts, which Minerva invented, and taught Vulcan and his Cyclops to make for Jupiter.