The goddess Artemis punished Agamemnon for killing a deer in her sacred grove and boasting that he was – compared to the goddess – the better hunter: at the beginning of the Trojan War, she prevented the Greek fleet from continuing to Troy under Agamemnon’s command by Aulis by bringing about a calm. The seer Kalchas prophesied that Agamemnon would have to sacrifice his daughter Iphigenia to the goddess in atonement in order to be able to continue his journey.
Following one version of this story, Agamemnon did as he was told. According to another, a doe was sacrificed instead and Iphigenia was raptured by Artemis to the land of the Taurians (compare the sacrifice of Isaac by Abraham) to serve her there as a priestess in the temple of Artemis.
Iphigenia appears in Euripides’ story of her brother Orestes. In order to escape the persecution by the Erinyes because of the murder of his mother Klytaimnestra and her lover Aigisthos (i.e. after the end of the Trojan War), Apollo ordered him to go to Tauris to fetch the wooden statue of Artemis that fell from the sky and bring her to Athens.
With his friend Pylades, the son of Strophios, Orestes travels to the Taurern, where the locals take both prisoners in order to sacrifice them – like all foreigners – to Artemis. The Artemis priestess, whose job it is to carry out the sacrifice, is his sister Iphigenia, who Orestes does not recognize. She offers to release him if he brings a letter from her to Greece. Orestes refuses, he wants to stay in Tauris and allow himself to be killed, but at the same time suggests that Pylades should run the errand. After a dispute between Orestes and Pylades, Orestes finally agrees to the proposal. The letter then reveals the relationship between Orestes and Iphigenia, the three of them flee Tauris, taking the picture of Artemis with them.
On his return to Greece, Orestes took possession of Mycenae, the kingdom of his father Agamemnon, to which he added Argos and Laconia. Iphigenia becomes a priestess of the Artemis sanctuary in Brauron.
Iphigenia, mentioned late in Greek mythology (only after the stories of Agamemnon and Clytaimnestra were recorded), became so closely associated with Artemis that some interpreters believe she was originally a rival goddess of hunting whose cult later was later merged with Artemis.
Hesiod reports that she became the goddess Hecate.
(Quoted from http://de.wikipedia.org/wiki/Iphigenie)