The Kerykes were one of the sacred Eleusinian families of priests that ran the Eleusinian Mysteries

Eleusinian Mysteries

The Eleusinian Mysteries were initiation ceremonies held every year for the cult of Demeter and Persephone based at Eleusis in ancient Greece. Of all the mysteries celebrated in ancient times, these were held to be the ones of greatest importance...

 during the Hellenic era. They popularized the cult

Cult

The word cult in current popular usage usually refers to a group whose beliefs or practices are considered abnormal or bizarre. The word originally denoted a system of ritual practices...

 and allowed many more to be initiated into the great secrets of Demeter

Demeter

In Greek mythology, Demeter is the goddess of the harvest, who presided over grains, the fertility of the earth, and the seasons . Her common surnames are Sito as the giver of food or corn/grain and Thesmophoros as a mark of the civilized existence of agricultural society...

 and Persephone

Persephone

In Greek mythology, Persephone , also called Kore , is the daughter of Zeus and the harvest-goddess Demeter, and queen of the underworld; she was abducted by Hades, the god-king of the underworld....

. Starting about 300 BC

300 BC

Year 300 BC was a year of the pre-Julian Roman calendar. At the time it was known as the Year of the Consulship of Corvus and Pansa...

, the state took over control of the Mysteries, specifically controlled by two families: the Eumolpidae

Eumolpidae

The Eumolpidae were a family of priests at Eleusis who maintained the Eleusinian Mysteries during the Hellenic era. As hierophants, they popularized the cult and allowed many more to be initiated into the secrets of Demeter and Persephone....

 and the Kerykes. This led to a vast increase in the number of initiates. The only requirements for membership were a lack of "blood guilt" (meaning having never committed murder

Murder

Murder is the unlawful killing, with malice aforethought, of another human being, and generally this state of mind distinguishes murder from other forms of unlawful homicide...

) and not a barbarian

Barbarian

Barbarian and savage are terms used to refer to a person who is perceived to be uncivilized. The word is often used either in a general reference to a member of a nation or ethnos, typically a tribal society as seen by an urban civilization either viewed as inferior, or admired as a noble savage...

 (i.e. Greek and able to speak Greek). Men, women and even slaves

Slavery

Slavery is a system under which people are treated as property to be bought and sold, and are forced to work. Slaves can be held against their will from the time of their capture, purchase or birth, and deprived of the right to leave, to refuse to work, or to demand compensation...

 were allowed to be initiated

Initiation

Initiation is a rite of passage ceremony marking entrance or acceptance into a group or society. It could also be a formal admission to adulthood in a community or one of its formal components...

.

Kerykes, which means in Greek heralds, were also part of the ritual and competitors at the Olympic Games (see Herald and Trumpet contest

Herald and Trumpet contest

In the 96th Olympiad , beside the athletic and artistic competitions, the "Herald and Trumpet contest" was added, which was already a formal element of the Olympic ritual performed by the kerykes and salpinktai . Winners were chosen by the clarity of the enunciation and the audibilty of their...

).