The Formorian King: Balor

Balor, King of the dark, demonic race called the Formorians; the oppressors of the Tuatha De Danann. In his youth he spied on his fathers druids whilst they concocted a spell of death, some of which got into his eye. Since being stung by the power of death, Balor's eye became a powerful tool in battle as it could kill all it beheld.
Balor stole Glas Ghoibhneann, a magical cow belonging to Cian of the Tuatha De Danann and proudly wore its skin upon his shoulders and enjoyed its velvety milk for many years before being slain by his own grandson, Lugh. Balor can often be seen wearing the skull of an elk, probably to hide his monstrous eye.