Eagle  

"And ready-witted Prometheus he bound with inextricable bonds, cruel chains, and drove a shaft through his middle, and set on him a long-winged eagle, which used to eat his immortal liver; but by night the liver grew as much again everyway as the long-winged bird devoured in the whole day."-- Theogony by Hesiod, Hugh G. Evelyn-White translation

The winged dog of Zeus, the tawny eagle,
Shall make thy flesh but a great rag to tear.
To ravin piecemeal, constant to his hour,
A guest unbidden, steadfast all day long.
Gorging thy liver, banquet black and rich.

--Prometheus Bound, Edwyn Bevan translation