Artemis
(Diana)

Artemis is Apollo's twin sister, the daughter of Zeus and Leto:

And Leto joined in love with Zeus who holds
The aegis, and the offspring which she bore
Were lovelier than all the sons of Heaven:
Apollo and the huntress Artemis.
-- Hesiod, Theogony (trans. Dorothea Wender)

Artemis is sometimes called "Cynthia," a name derived from the place of her birth, Mount Cynthus, in Delos. She is also said to have been born at Ortygia.

"She was the Lady of Wild Things, Huntsman-in-chief to the gods, an odd office for a woman. Like a good huntsman, she was careful to preserve the young; she was 'the protectress of dewy youth' everywhere."
-- Edith Hamilton.

Artemis protects her own, but she is a goddess to be feared, and her skillful aim with a bow brings pain and death to those who incite her wrath.

As Apollo was associated with the sun, so Artemis was associated with the moon. This brought her into connection with Hecate, the goddess of necromancy and all other forms of sorcery and magic arts. Because Hecate is also associated with the moon, the two goddesses ultimately became confounded so that, in later accounts especially, they are represented as one and the same goddess under different names.

Although worshipped in many places, her most famous shrine is in Ephesus. When the missionary activity of the Apostle Paul roused to fury certain Ephesians and brought the whole city into a state of confusion, the town clerk calmed the citizens with the reassurance, "All the world knows that our city of Ephesus is temple-warden of the great Diana and of that symbol of her which fell from heaven" (Acts 19.23ff).

An Artist's Depiction of the Temple of Artemis at Ephesus