The Homeric Hymn to Demeter informs us, that in Eleusis Eumolpos belonged to the chiefs among the people. Because he was "blameless" and "daughty" Demeter taught him, together with the other leaders - Triptolemus, Diocles, Keleus and Polyxeimus - all her mysteries. Pausanias says, that Eumolpus performed the holy rites of two goddesses with the daughters of Keleus. He became the first priest of the Eleusinian mysteries, ancestor of a hierophant. He was excellent in singing and also in music, playing a lyre and a flute, which whom he took the first place during the Pelios funeral games. They say, that Eumolpus was teaching Heracles in the art of music and songs. His devotion was a reason that the dying king Tegyrios forgave him at the end and offered him the Thracian throne.
When the battle between Athens and Eleusis began, Eumolpus sent many Thracian warriors to help Eleusis. Their leader was his son Himmarados, who was killed by the Athenian king Erechtheus. The other version of the myth is telling us, that Erechtheus was the killer of Eumolpos and that his father Poseidon asked Zeus to take revenge. Zeus annihilated Erechtheus by a lightning, but some authors are describing, that Poseidon knocked him down in Makra and that the earth was opened to swallow him.
The Eleusinians lost their independence in the battle with Athens, nevertheless they retained the privilege carrying on the Mysteries. After the death of Eumolpos the place of the high priest was occupied by his younger son Herald-Keryx, so the line of priestsī family Eumolpides in Eleusis began. But Pausanias says, that Heralds themselves believed, he was a son of Hermes and Aglauros, daughter of Kekrops.
With the myth about Eumolpus are connected several Athenian mythical stories to show an important position of Eleusis, their leaders and high priests, who originated from gods and had relations with the legendary king families.
Eumolpus is depicted, but not very often, on some Greek vases. He appears (included with an inscription) on the Red figure skyphosvase, attributed to Makron, dated to ca 490-480 BCE, exhibited in the British Museum in London. The name of Eumolpus was found on three vases from the fifth century BCE. Some scholars believe, that Eumolpus is represented also in the scene with Heracles on the so called Pourtales vase from the British Museum.