King of Gwynedd 634-655
His exact origins are uncertain as are the circumstances in which he came to power. He may well have been acting as Cadwallon's regent whilst the latter was busy ravaging Northumbria and took advantage of Cadwallon's death at the battle of Heavenfield and the extreme youth of Cadwallon's son Cadwaladr to seize the throne of Gwynedd for himself.
Cadfael continued Cadwallon's policy of alliance with Mercia, and fought alongside Penda in the battle of Winwaed or Winwidfeld in 655, when Penda was defeated and killed by Oswiu of Bernicia. Cadfael managed to escape but Cadwaladr seems to have taken this opportunity to return from exile and reclaim the throne.
It is not known what happened to Cadfael after this. He may have been killed by Cadwaladr when the latter took power, or he may simply have disappeared into exile somehwere.