archetypal barbarian, stereotypically presented as massive, powerful, and malicious. One of the practices of the Celts that the Greco-Roman civilizations found especially barbaric was headhunting. Celts were described by Greco-Roman writers as having a "cult of the severed head" and human sacrifice as major components of their religious life. Celts followed an ancient Celtic religion overseen by the Druids. According to Paul Jacobsthal, "Amongst the Celts the human head was venerated above all else, since the head was to the Celt the soul, centre of the emotions as well as of life itself, a symbol of divinity and of the powers of the other-world." Ancient Romans and Greeks recorded the Celts' habits of embalming in cedar oil the heads of the most distinguished enemies, allies and relatives; and the mounting of the heads on walls for decoration and in porticos or pillars in their entry for display. The Greco-Roman writers also describe the Celts hanging severed heads from the necks of their horses while riding in order to intimidate onlookers and enemies alike. If Irish mythology is to be believed, headhunting and a beheading game may have been practiced in Ireland for a great deal longer by the Celtic Gaels, perhaps all the way to the introduction of Christianity to Ireland in the 5th century AD. In the Ulster Cycle of Irish mythology, two of the major heroic figures, Cúchulainn and Conall Cernach, are both described as taking part in this practice. With both heroes decapitating their enemies and publicly displaying the heads. Both the Greeks and Romans found the Celtic decapitation practices shocking, and the Romans made sure to put an end to them when Celtic regions came under their control. However, Greeks and Romans both employed decapitation and other horrific tortures, highlighting a tendency to view practices as more shocking when carried out by an outside group, even if the practices were essentially similar. In the 5th century BC, Greek writer Ephoros described the Celts as "one of the four great barbarian peoples, along with the Persians, the Scythians and the Libyans". They were called Keltoi or Galatae by the Greeks and Celtae or Galli by the Romans. Aristotle comments that their courage had an element of passion to it, like that of all barbarians. Diodorus Siculus writes that they were extremely addicted to wine and that one could exchange a mere jar of wine for a slave.