Son of Mynyo.
As a warrior and messenger for King Arthur, Iddawg deliberately caused the Battle of Camlann between Arthur and Mordred when he delivered a peace message from Arthur to Mordred in rude and insulting tones. For this, he became known as "the Churn of Britain" ('the Embroiler of Britain').
After the fateful battle, he did penance in Scotland for his deeds. Rhonabwy met Iddawg in his epic dream, and Iddawg became his guide in the times of Arthur, seven hundred years before Rhonabwy’s life.