Diarmait mac Cerbaill (died c. 565) was King of Tara or High King of Ireland. According to traditions, he was the last High King to follow the pagan rituals of inauguration, the ban-feis or marriage to goddess of the land.
While many later stories were attached to Diarmait, he was a historical ruler and his descendants were of great significance in Medieval Ireland.
Read more about Diarmait Mac Cerbaill: Sources, Ireland in The 6th Century, Grandsons of Neill, Tribe of Conn, Reign, Saints and Druids, Aided Diarmata, Descendants