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.