Medusa

Origin: Medusa (greek for "guardian") is a monster that originated in the oral and literary tradition of greek mythology. She is the daughter of Phorcys and Ceto, and the only one of the three Gorgons subject to mortality. According to Apollodorus, Medusa and her sisters were born with viperine locks, yellow wings, and skin lined with impenetrable scales. In Ovid's later conception of Medusa, she was fancied by Poseidon and subsequently raped by him in Athena's temple; the jealous and enraged goddess in turn transformed her locks into serpents and left her with a most abject face. In most accounts, she was slain by the hero Perseus, who used a shield gifted by Athena as his primary weapon for reflecting her gaze. He used her removed head as a weapon, but at some point bestowed it to Athena, which was then affixed to her own shield.

The fact that Medusa can't be confronted face to face because of her abject appearance and petrifying stare, is what defines her as the embodiment of what can't be concretely represented, ie. Death. Death is an abstract concept that exists in a realm beyond our experience, thus it's unfathomable. Like Hades, she was impossible to look at. Medusa's tragic duality, her beauty cursed with a mask of lurid ugliness, establishes her also as a symbol of ambiguity.

Other facts:

- Medusa's face represented that of a warrior consumed by battle frenzy. In The Shield of Heracles (232-3), Hesiod describes the wide-open mouth, the fearsome hair and the Gorgons' shrill cries which conjure up her terrifying aspect. 

- She is the guardian of terrifying places, either the nocturnal borders of the world or the Underworld. She reappears in this role in Dante's Divine Comedy (Inferno, IX, 55-7) and Milton's Paradise Lost (II, 611). Guarding the doorway to the world of the dead, she prevents the living from entering.