POLYBOIA (Polyboea) was a maiden of Amyklai (Amyclae) near Sparta who was granted immortality as a demi-goddess in the train of Artemis. Her name means "Many-Cows" which is an archaic reference to her beauty and worth--for suitors once paid a bride-price in cattle.
Polyboia was perhaps identified with Phylonoe, a similar Spartan demi-goddess. According to Hesychius she was also identified with Artemis and Persephone.
AMYKLAS & DIOMEDE (Pausanias 3.19.4)
CLASSICAL LITERATURE QUOTES
Pausanias, Description of Greece 3. 19. 4 (trans. Jones) (Greek travelogue C2nd A.D.) :
"[Amongst the scenes depicted on the altar of Apollon at Amyklai (Amyclae) near Sparta :] On the altar are wrought in relief . . . the Moirai (Fates) and Horai (Seasons), and with them Aphrodite, Athena and Artemis. They are carrying to heaven Hyakinthos (Hyacinthus) and Polyboia (Polyboea), the sister, they say, of Hyakinthos, who died a maid."
- Pausanias, Description of Greece - Greek Travelogue C2nd A.D.
Other references not currently quoted here: Hesychius s.v. Polyboia.