Eleusinian Mysteries

The Eleusinian Mysteries () were a series of initiations held every year in honor of the Greek goddesses Demeter and Persephone. They were held at or near the city of Eleusis. They are the "most famous of the secret religious rites of Ancient Greece". Some think the power of the Eleusinian Mysteries came from drinking a psychedelic potion called "kykeon". 
The mysteries were about the myth of the abduction of Persephone from her mother Demeter by Hades, the god of the underworld. This myth had a cycle of three phases: the "descent" (loss), the "search", and the "ascent". The main theme was the "ascent" (άνοδος) of Persephone to the mortal realm and her reunion with her mother. 
Those who took part in these mysteries were sworn to secrecy. Initiates were promised a reward in the afterlife. It was a major festival of the Hellenic era, and later spread to Rome. Similar religious rites appear in the agricultural societies of the Near East and in Minoan Crete.