The kingdom rose to power under their king Aedan mac Gabrain. He became their king in 574. In 603 Aedan led his people against Athelfrith of Bernicia at a place called "Degsastan." The Scots were completely defeated. Defeats in Ireland and Scotland during the reign of Domnall Brecc (d. 642) ended Dál Riata's dominance. The kingdom came under the control of Northumbria, then subject to the Picts. The kingdom's independence ended in the Viking Age, as it merged with the lands of the Picts to form the Kingdom of Alba.