An ancient form of Rip van Winkle. Legend has it he fell asleep in a cave while tending his sheep and woke up 57 years later.
Epimenides was said be have been originally from Knossos in Crete and his notable achievement after waking up was cleansing Athens of a plague that had befallen the city following a violation of Athena's sanctuary. His most lasting claim to fame is the statement known as the Epimenides paradox.
The story is quite confused and, while Epimenides may have been an actual figure, all the stories surrounding him weren't necessarily real. One version of the legend mentions tattoos on his body, which were not used except for slaves in Greece but were fairly common among the elite in Thrace and Asiatic tribes further north and east. He was more likely a medley of more than one actual persons, one more palatable local hero and one shaman from the far north. The long sleep of Epimenides can be compared to a shaman's retreat which may involve a condition resembling a long sleep. Descriptions of him being able to separate his soul from his body at will match what we know today as astral projection rather precisely.
Another clue is the claim of being a reincarnation of Aeacus, another figure related to cleansing from plague. While belief in reincarnation was uncommon in ancient Greece, it was and is widespread in cultures farther east and may have been a concept in an earlier, indigenous religion.
All in all, the tale and the figure of Epimenides are a make what you want of it thing, but there is definitely something apocryphal about it and he is frequently studied in contemporary occultist writings. The figure may be associated with an indigenous deity superseded by the Olympian gods.