The Eleusinian Mysteries were the most sacred and secret religious rites in ancient Greece.
According to their mythological explanation, the Mysteries were established by Goddess Demeter and those who were successfully initiated would no longer fear death.
Demeter and her daughter, Persephone, were central characters in the Eleusinian Mysteries, where initiates would accomplish rites from 1600 BCE to 392 CE.
Every year in spring time , the Ancient Athenians would celebrate this renaissance with the mystical Eleusinian festivals.
The Eleusinians were a secretive school in Eleusis in the northwest of Athens dedicated to celebrate Demeter and Persephone, there was different degrees of initiation.
It is only known that during these rituals the initiates would be given such a vivid vision of their afterlife that it would free them from the fear of death as they understood that the soul stay intact through a continuous change of mortal bodies.
Prominent men of antiquity, like Plato, Pythagoras and Roman Emperor Hadrian, were initiated into the Mysteries.
The Mysteries have managed to keep their secrets and till today no one really knows what was really taking place inside the adyton, the inner chamber of the Temple.
For a good reason : speaking about the mysteries was punishable by death.
The mystery is intact.