In most internet sources it says Zeus, Hera, Poseidon, Demeter, Ares, Hermes, Hephaestus, Aphrodite, Athena, Apollo, and Artemis are always considered to be Olympians and either Hestia or Dionysus is added to the list. Hades is not considered an Olympian as he lives in the underworld. But in 'Mythology' by Edith Hamilton it says that Hades is an Olympian. Demeter and Dionysus are not included in the list and are referred to as 'two great gods of earth'. So which list of the 12 Olympians is correct?