The Centaurs were half-man half-horse creatures. Their upper half was human, while their lower half had four legs like a horse. In general, centaurs were loud and vulgar. However, one centaur named Chiron was intelligent and skilled in training. He trained many of the Greek heroes including Achilles and Jason of the Argonauts.
Cerberus
The Cerberus was a giant three-headed dog that guarded the gates of the Underworld. Cerberus was the offspring of the feared monster Typhon. Hercules had to capture Cerberus as one of his Twelve Labors.
Charybdis
Charybdis was a sea monster that took the shape of a giant whirlpool. Any ships that came near Charybdis were pulled down to the bottom of the sea. Ships that passed through the Strait of Messina had to either pass by Charybdis or face the seas monster Scylla.
Chimera
The chimera was a giant monster that was a combination of many animals including a goat, lion, and snake. It was an offspring of Typhon. The Chimera was feared throughout Greek mythology as it could breathe fire.
Cyclopes
The Cyclopes were one-eyed giants. They were famous for making Zeus his thunderbolts and Poseidon his trident. Odysseus also came into contact with a Cyclops while on his adventures in the Odyssey.
Furies
The furies were flying creatures with sharp fangs and claws who hunted down murderers. There were three main furies who were sisters: Alecto, Tisiphone, and Magaera. The "Furies" is actually a Roman name. The Greeks called them the Erinyes.
Griffins
The griffin was a combination of a lion and an eagle. It had the body of a lion and the head, wings, and talons of an eagle. Griffins were said to live in northern Greece where they guarded a huge treasure.
Harpies
The harpies were flying creatures with the faces of women. The harpies are famous for stealing the food of Phineus every time he tried to eat. Jason and the Argonauts were going to kill the harpies when the goddess Iris intervened and promised that the harpies would not bother Phineus any longer.
Hydra
The hydra was a fearsome monster from Greek Mythology. It was a giant snake with nine heads. The problem was that if you cut one head off, more heads would quickly grow back. Hercules slew the hydra as one of his Twelve Labors.
Medusa
Medusa was a type of Greek monster called a Gorgon. She had a woman's face, but had snakes for hair. Anyone who looked into Medusa's eyes would be turned to stone. She was once a beautiful woman, but was turned into a Gorgon as punishment by the goddess Athena.
Minotaur
The Minotaur had the head of bull and the body of a man. The Minotaur came from the island of Crete. He lived underground in a maze called the Labyrinth. Each year seven boys and seven girls were locked into the Labyrinth to be eaten by the Minotaur.
Pegasus
Pegasus was a beautiful white horse that could fly. Pegasus was the horse of Zeus and the offspring of the ugly monster Medusa. Pegasus helped the hero Bellerophon to kill the chimera.
Satyrs
Satyrs were half-goat half-man. They were peaceful creatures who loved to have a good time. They also liked to pull pranks on the gods. The Satyrs were associated with the god of wine, Dionysus. The satyr Silenus was perhaps the most famous satyr. He was the son of the god Pan.
Scylla
Scylla was a terrible sea monster with 12 long tentacle legs and 6 dog-like heads. She guarded one side of the Strait of Messina while her counterpart Charibdis guarded the other side.
Sirens
The Sirens were sea nymphs who lured sailors to crash on the rocks of their islands with their songs. Once a sailor heard the song, he could not resist. Odysseus encountered the Sirens in his adventures on the Odyssey. He had his men put wax in their ears so they could not hear the song, then he tied himself to the ship. This way Odysseus could hear their song and not be captured.
Sphinx
The Sphinx had the body of a lion, the head of a woman, and the wings of an eagle. The Sphinx terrorized the city of Thebes, killing all those who could not solve its riddle. Finally, a young man named Oedipus solved the Sphinxes riddle and the city was saved.
Typhon
Typhon was perhaps the scariest and most powerful of all the monsters in Greek Mythology. He was called the "Father of all monsters" and even the gods were scared of Typhon. Only Zeus could defeat Typhon. He had the monster imprisoned underneath Mount Etna.