Zeus

Zeus was, in Greek mythology, the leader of the gods. He was a fatherly figure, and the actual father of a number of his fellow deities including Apollo, Athena, Artemis, Castor and Pollux, Dionysius, Hebe, Heracles, Minos, Hermes, Persephone, (PROSE: Deadly Reunion) and Ares. (PROSE: The Lost Ones) His powers were associated with lightning. (TV: The Time Monster, COMIC: The Life Bringer!)

As with the rest of the Greek pantheons, multiple accounts showed that Zeus was a real being with whom the Doctor had dealings, but disagreed as to the details, with him variously construed as an Immortal (PROSE: Deadly Reunion) or an Olympian. (COMIC: The Life Bringer!)

Origins
According to one account, Zeus and the other Greek deities were Immortals, a race of powerful immortal humanoids who were native to Earth and believed to be an offshoot of humanity; while Zeus and his kin were worshipped as gods, other Immortals in other eras were thought of as witches. (PROSE: Deadly Reunion) According to another account, Zeus and his pantheon were Olympians, native to a planet called Olympus; though they had influenced the Earth, they were not native to it nor residents of it. (COMIC: The Life Bringer!)

Banishing Prometheus
After his fellow Olympian Prometheus stole life spores and spread them across the galaxy to create life, Zeus became angry and banished him to an unknown planet, to be chained to a mountain for the rest of his existence. Zeus believed that the life spores should only be used once, to produce peace-loving creatures. (COMIC: The Life Bringer!)

Meeting the Fourth Doctor
When Prometheus returned to Olympus with the Fourth Doctor and K9 to the planet Olympus, Zeus sent Aphrodite to bring them to him. Prometheus tried to reason with Zeus that people were good but Zeus mentioned that most of them knew how to hate, steal, kill, and start wars; they had poisoned the universe with their actions. He had Prometheus sent to the confinement rooms whilst the Doctor and K9 were sent to Asclepius to be studied.

After the Doctor, K9, and Prometheus escaped, Zeus showed his wrath by appearing in a gigantic form in the clouds. He sought to stop them by attacking them with massive amounts of electricity. However, once they got into the TARDIS, Zeus wasn't able to destroy the ship with his powers. (COMIC: The Life Bringer!)

Retirement
He retreated from Earth to an alternate dimension sometime before the 20th century. Demeter tried to contact him to stop Hades from taking over the world. Though it was not immediate, Zeus finally returned and banished Hades to the underworld forever. Demeter and her family decided to leave with Zeus when he went back to the alternate dimension. (PROSE: Deadly Reunion)

Legacy
The First Doctor was mistaken for Zeus by the Greeks during the Trojan War in circa 1200 BC as well by the Trojan servant Katarina, who became one of his companions. (TV: The Myth Makers)

Hippias called a lightning bolt "a sphere of fire hurled by the hand of Zeus." (TV: The Time Monster)

Bigon once swore by Zeus. (TV: Four to Doomsday)

Both Axatil and his captain frequently swore by Zeus. (PROSE: The Lost Ones)

A belief engine once fell to Earth in ancient Greece in Socrates's day. The faith of the locals created a psychic construct version of Zeus, but he vanished when Socrates logically proved to him that he did not really exist. (COMIC: The Chains of Olympus)

A statue of Zeus at Olympia was one of the Seven Wonders of the World. Like the other six Wonders, it was stolen by Pholonius Ginn, who intended on selling it to the highest bidder on G-Bay. It was later returned by Trongus Squum, at the Tenth Doctor's request. (COMIC: Minus Seven Wonders)