Cormac mac Airt

In Goidelic Celtic mythology, Cormac mac Airt was the son of Achtan and Airt. He may have been a historical Irish king. He ruled from Tara, the capital of the High Kings of Ireland for forty years, probably AD 227 to 266.

The sea god Manannan Mac Lir gave him a magical gold goblet. It would break into three pieces when three lies were told over it; speaking three truths would fix it.