Lycaon is an exceptionally antagonistic figure in Greek mythology who tested the might of Zeus and was severely punished for his transgressions - his name may have given rise to the term "lycanthropy".
In the most popular version of the myth, Ovid's Metamorphoses, Lycaon was the cruel king of Arcadia, son of Pelasgus and Meliboea. Angered by Zeus' visit being celebrated, Lycaon served him a dish of a slaughtered and dismembered child (in some versions, his son, Nyctimus, and in other versions, his infant grandchild, Arcas) in order to see whether or not Zeus was truly omniscient. Even when offering Zeus the "meal", Lycaon took a taste of it himself. In his quest to test Zeus' immortality, Lycaon attempted to murder the god while he slept. In return for these gruesome deeds, Zeus transformed Lycaon into the form of a wolf, causing him to go on a rampage and slaughter several sheep, and killed Lycaon's fifty sons by lightning bolts, except possibly Nyctimus, who was then the slaughtered child, and instead became restored to life.