Palladion
The Palladion (more often spelled Palladium) was a xoanon (wooden effigy) of Athena Polias (Protectress of the City) that fell from heaven according to myth. It was kept in the Polias precinct of the Erechtheum temple on the Acropolis of Athens and was considered the most sacred cult object on the hill by far. Once a year it was ceremonially taken to Phaleron Bay by the priestesses, was washed in the sea and was returned to the temple by procession. This marked the festival of the "Plynteria" (the Washing).
There are two legends about its origin: according to one, Athena made the effigy in memory of her playmate Pallas (Παλλάς), whom she accidentally killed during sparring practice. According to the other, it was made after Athena killed the rebel Titan Pallas in battle, for which victory she acquired the title "Athena Pallas" (Αθηνά Παλλάς).
The Palladion had survived in the early Christian era and was shown to a bishop who described it as a "blackened, shapeless stake of wood".