most of whom were vassals of the Ulaid before casting off Ulaid overlordship and becoming independent. It has been suggested that the Airthir—in whose lands lay Emain Macha—were originally an Ulaid tribe before becoming one of the Airgíalla. Towards the end of the 5th century, the Ulaid sub-group Dál Riata, located in the Glens of Antrim, had started settling in modern-day Scotland, forming a cross-channel kingdom. Their first settlements were in the region of Argyll, which means "eastern province of the Gael". It is to these boundaries that Ulaid entered the historic period in Ireland in the 6th century, though the Dál nAraidi still held territory west of the Bann in County Londonderry. The emergence of the Dál nAraidi and Dál Fiatach dynasties may have concealed the dominance of earlier tribal groupings. 6th to 7th centuries By the mid-6th century, the Dál Riata possessions in Scotland came under serious threat from Bridei I, king of the Picts, resulting in them seeking the Northern Uí Néill's aid. The king of Dál Riata, Áedán mac Gabráin, had already granted the island of Iona off the coast of Scotland to the Cenél Conaill prince and saint, Columba, who in turn negotiated an alliance between the Northern Uí Néill and Dál Riata in 575 at Druim Ceit near Derry. The result of this pact was the removal of Dál Riata from Ulaid's overlordship allowing it to concentrate on extending its Scottish domain. That same year either before or after the convention of Druim Ceit, the king of Dál Riata was killed in a bloody battle with the Dál nAraidi at Fid Euin. In 563, according to the Annals of Ulster, an apparent internal struggle amongst the Cruthin resulted in Báetán mac Cinn making a deal with the Northern Uí Néill, promising them the territories of Ard Eólairgg (Magilligan peninsula) and the Lee, both west of the River Bann. As a result, the battle of Móin Dairi Lothair (modern-day Moneymore) took place between them and an alliance of Cruthin kings, in which the Cruthin suffered a devastating defeat. Afterwards the Northern Uí Néill settled their Airgíalla allies in the Cruthin territory of Eilne, which lay between the River Bann and the River Bush. The defeated Cruthin alliance meanwhile consolidated themselves on Dál nAraidi. The Dál nAraidi king Congal Cáech took possession of the overlordship of Ulaid in 626, and in 628 killed the High King